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

Abstract

The present disclosure relates to the technical field of batteries, and in particular, to a porous carbon material, a silicon-carbon negative electrode material and a preparation method therefor and a use thereof. The porous carbon material has a surface functional group. The surface functional group comprises an alkaline functional group, a neutral functional group, and an acidic functional group. The content of the surface functional group is 0.4-1 mmol / g, the content of the alkaline functional group is 0.2-0.5 mmol / g, the content of the neutral functional group is 0.2-0.4 mmol / g, and the content of the acidic functional group is less than 0.2 mmol / g. The surface of the porous carbon material of the present disclosure has the appropriate contents and types of functional groups, so that the porous carbon has high conductivity and appropriate wettability, thereby improving the silicon utilization rate of the silicon-carbon negative electrode material and improving the cycle performance and rate performance thereof.

Description

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

[0001] Cross-reference to Related Applications

[0002] The present application claims priority to the Chinese patent application No. 2024113770802, filed on September 30, 2024, and entitled "Porous carbon material, silicon-carbon negative electrode material, and preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of batteries, in particular, to a porous carbon material, a silicon-carbon negative electrode material, and a preparation method and application thereof. BACKGROUND

[0004] Lithium ion batteries have been widely used in the fields of electric vehicles, mobile devices, etc. One of the key factors affecting the electrical performance of lithium ion batteries is the negative electrode material. Existing commercial negative electrode materials include mesocarbon microbeads and modified graphite, but have the disadvantages of low theoretical lithium storage capacity, easy organic solvent co-intercalation, etc.

[0005] Among the current lithium storage materials, silicon has the highest theoretical capacity (4200 mAh / g), but the silicon negative electrode material has a huge volume change during the charging and discharging process of the battery, which leads to the shedding and pulverization of the electrode active material, and even causes damage to the electrode structure, resulting in rapid decay of the battery capacity, which seriously restricts its industrial application. In the prior art, silicon and carbon materials are compounded to obtain a silicon-carbon composite material to alleviate the volume change of silicon during the charging and discharging process. However, the utilization rate of silicon in the preparation process of the current silicon-carbon negative electrode material is poor, and the electrical performance of the silicon-carbon negative electrode material is not ideal.

[0006] Therefore, the present disclosure is proposed.

[0007] SUMMARY

[0008] One object of the present disclosure is to provide a porous carbon material to solve the technical problems of poor utilization rate of silicon and non-ideal electrical performance of the silicon-carbon negative electrode material in the prior art. The porous carbon of the present disclosure has suitable content and types of surface functional groups, which is beneficial to improve the utilization rate of silicon in the silicon-carbon material and improve the electrical performance of the silicon-carbon material.

[0009] Another object of the present disclosure is to provide a silicon-carbon negative electrode material with high electrical conductivity, high capacity, and high cycle performance.

[0010] Another object of the present disclosure is to provide a preparation method of a silicon-carbon negative electrode material, which is simple and easy to implement, and the obtained silicon-carbon negative electrode material has excellent electrical performance.

[0011] In order to achieve the above object of the present disclosure, the following technical solutions are adopted:

[0012] A porous carbon material, wherein the porous carbon material has surface functional groups, the surface functional groups comprising basic functional groups, neutral functional groups and acidic functional groups; the content of the surface functional groups is 0.4-1 mmol / g, the content of the basic functional groups is 0.2-0.5 mmol / g, the content of the neutral functional groups is 0.2-0.4 mmol / g, and the content of the acidic functional groups is less than 0.2 mmol / g.

[0013] In some embodiments, the content of the surface functional groups is 0.4-0.7 mmol / g, wherein the content of the basic functional groups is 0.2-0.5 mmol / g, the content of the neutral functional groups is 0.2-0.4 mmol / g, and the content of the acidic functional groups is less than 0.1 mmol / g.

[0014] In some embodiments, the basic functional groups comprise carbonyl groups, the neutral functional groups comprise phenolic hydroxyl groups, and the acidic functional groups comprise hydroxyl groups and carboxyl groups.

[0015] In some embodiments, the electrical conductivity of the porous carbon material is 2-5 S / mm.

[0016] In some embodiments, the pH of the porous carbon material is 6.8-8.

[0017] In some embodiments, the particle size Dv50 of the porous carbon material is 3-10 μm.

[0018] In some embodiments, the particle size Dv99 of the porous carbon material is 10-25 μm, and the particle size Dn10 of the porous carbon material is 0.5-5 μm.

[0019] In some embodiments, the specific surface area of the porous carbon material is 1000-2200 m 2 / g.

[0020] In some embodiments, the pore volume of the porous carbon material is 0.6-1.2 cm 3 / g.

[0021] In some embodiments, the microporosity of the porous carbon material is 50%-100%.

[0022] A silicon-carbon negative electrode material, comprising the porous carbon material and nano-silicon particles in the pores of the porous carbon material.

[0023] In some embodiments, the mass content of the nano-silicon particles in the silicon-carbon negative electrode material is 5%-85%.

[0024] In some embodiments, 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.

[0025] In some embodiments, the specific surface area of the silicon-carbon negative electrode material is less than 3 m 2 / g.

[0026] In some embodiments, the electrical conductivity of the silicon-carbon negative electrode material is 0.2-2 S / mm.

[0027] In some embodiments, 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.

[0028] The preparation method of the silicon-carbon negative electrode material comprises the following steps:

[0029] The porous carbon material is subjected to vapor deposition in an atmosphere containing a silicon source to obtain the silicon-carbon negative electrode material.

[0030] In some embodiments, 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, fast ion conductor and high molecular polymer.

[0031] An electrode comprises the silicon-carbon negative electrode material.

[0032] A lithium ion battery comprises the electrode.

[0033] An electrical device comprises the lithium ion battery. DETAILED DESCRIPTION

[0034] The embodiments of the present disclosure will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present disclosure and should not be regarded as limiting the scope of the present disclosure. The specific conditions are not specified in the examples, 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 all conventional products that can be obtained by purchase.

[0035] According to one disclosure of the present disclosure, the present disclosure relates to a porous carbon material having surface functional groups, wherein the surface functional groups comprise basic functional groups, neutral functional groups and acidic functional groups; the content of the surface functional groups is 0.4-1 mmol / g, the content of the basic functional groups is 0.2-0.5 mmol / g, the content of the neutral functional groups is 0.2-0.4 mmol / g, and the content of the acidic functional groups is less than 0.2 mmol / g.

[0036] The oxygen-containing functional groups on the surface of the carbon material can be divided into acidic functional groups (such as carboxyl, and also carboxylic anhydride), neutral functional groups (also known as weakly acidic functional groups, such as phenolic hydroxyl, epoxy, ether, etc.), and basic functional groups (such as quinone, carbonyl, etc.). The surface functional groups have a very important influence on the electrical conductivity, wettability of the material, and rate capability and cycle life. The present disclosure controls the surface of the porous carbon material to have a suitable content of functional groups, thereby ensuring high electrical conductivity, wettability, and stability of the porous carbon material. Since the rate of the silicon-carbon negative electrode material is significantly affected by the porous carbon, and the rate capability of the porous carbon material depends on the influence of the oxygen-containing functional groups on the ion diffusion and electrical conductivity of the carbon material, and the total content of the surface functional groups is often inversely proportional to the electrical conductivity (the decrease in electrical conductivity is due to the increase in defects, sp3 carbon, and impedance caused by the introduction of oxygen-containing functional groups); if the surface functional groups are too much, ion diffusion will be hindered, the rate capability will decrease, and the initial efficiency of the porous carbon material will decrease significantly; and complete oxygen removal will reduce the wettability of the porous carbon material; the presence of surface functional groups not only changes the hydrophobicity of the surface of the porous carbon material, but also provides adsorption sites for many reactions (hydrophilic groups such as hydroxyl and carboxyl), which can effectively improve the wettability of the carbon material and is more beneficial to the cycle life of the silicon-carbon negative electrode material. Therefore, the present disclosure controls the total content of the surface functional groups of the porous carbon material within the above suitable range, so as to facilitate the performance of the silicon-carbon negative electrode material. In some embodiments, the content of the surface functional groups of the porous carbon is 0.4-1 mmol / g, which can be, for example, but is not limited to, 0.4 mmol / g, 0.45 mmol / g, 0.5 mmol / g, 0.55 mmol / g, 0.6 mmol / g, 0.7 mmol / g, 0.8 mmol / g, 0.9 mmol / g, 1 mmol / g, etc., or a range value between any two of them.

[0037] Among the above-mentioned functional groups, carboxyl and hydroxyl groups are unstable functional groups, while carbonyl and phenolic hydroxyl groups are more stable. The redox reaction of unstable oxygen-containing functional groups is irreversible, which not only leads to rapid decay of the capacity contributed by the oxygen-containing functional groups, but also may block the pore structure of the porous carbon material, resulting in a significant decrease in the overall cycle stability of the silicon-carbon material. Therefore, the unstable groups are removed by high-temperature processes, so that the content of the acidic functional groups is less than 0.2 mmol / g, and the contents of the basic functional groups and the neutral functional groups are ensured to be within the above-mentioned suitable ranges, so that the content of the stable functional groups in the porous carbon material is greater than the content of the unstable functional groups, so as to make the porous carbon have high electrical conductivity and suitable wettability. In some embodiments, the content of the basic functional groups may be, but is not limited to, 0.2 mmol / g, 0.25 mmol / g, 0.3 mmol / g, 0.35 mmol / g, 0.4 mmol / g, 0.5 mmol / g, or a range value between any two of them; the content of the neutral functional groups may be, but is not limited to, 0.2 mmol / g, 0.25 mmol / g, 0.3 mmol / g, 0.35 mmol / g, 0.4 mmol / g, or a range value between any two of them; and the content of the acidic functional groups may be, but is not limited to, 0, 0.02 mmol / g, 0.05 mmol / g, 0.08 mmol / g, 0.1 mmol / g, 0.12 mmol / g, 0.15 mmol / g, 0.19 mmol / g, or a range value between any two of them.

[0038] In addition, the oxygen-containing functional groups on the surface of the porous carbon material can increase the adsorption sites, and the content and distribution of the functional groups have a significant influence on the adsorption of the porous carbon material. They usually increase the polarity of the surface of the porous carbon material, thereby enhancing the interaction with the silicon material molecules, which is beneficial to promoting adsorption and diffusion in the preparation of the silicon-carbon negative electrode material and to the preparation and performance of the silicon-carbon negative electrode material.

[0039] In some embodiments, the content of the surface functional groups is 0.4-0.7 mmol / g, wherein the content of the basic functional groups is 0.2-0.5 mmol / g, the content of the neutral functional groups is 0.2-0.4 mmol / g, and the content of the acidic functional groups is less than 0.1 mmol / g. The present disclosure further selects the content range of the total surface functional groups and the content ranges of the basic functional groups, the neutral functional groups, and the acidic functional groups, so as to more favorably coordinate to obtain a porous carbon material with high electrical conductivity, suitable wettability, and high stability.

[0040] In some embodiments, the electrical conductivity of the porous carbon material is 2-5 S / mm, for example, but not limited to, 2 S / mm, 2.2 S / mm, 2.5 S / mm, 2.8 S / mm, 3 S / mm, 3.2 S / mm, 3.5 S / mm, 3.8 S / mm, 4 S / mm, 5 S / mm, or a range value between any two of them. The porous carbon of the present disclosure has a high electrical conductivity, which lays a good foundation for obtaining a high electrical conductivity silicon-carbon negative electrode material subsequently, so as to improve the electrical performance of the silicon-carbon negative electrode material.

[0041] In some embodiments, the pH of the porous carbon material is 6.8-8, for example, but not limited to, 6.8, 6.9, 7, 7.1, 7.2, 7.5, 7.8, or 8, or a range value between any two of them. The surface functional groups of the porous carbon of the present disclosure mainly contain basic functional groups and neutral functional groups, and the pH of the obtained porous carbon is 6.8-8.

[0042] In some embodiments, the particle size Dv50 of the porous carbon material is 3-10 μm, for example, but not limited to, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range value between any two of them. The particle size Dv99 of the porous carbon is 10-25 μm, for example, but not limited to, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, or a range value between any two of them. The particle size Dn10 of the porous carbon is 0.5-5 μm, for example, but not limited to, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range value between any two of them. The porous carbon of the present disclosure has a suitable particle size, which is more conducive to ensuring the electrical performance of the porous carbon.

[0043] In some embodiments, the specific surface area of the porous carbon material is 1000-2200 m 2 / g, for example, but not limited to, 1000 m 2 / g, 1200 m 2 / g, 1500 m 2 / g, 1700 m 2 / g, 1800 m 2 / g, 2000 m 2 / g, 2100 m 2 / g, or 2200 m 2 / g, or a range value between any two of them. The porous carbon of the present disclosure has a suitable specific surface area, which is more conducive to ensuring its high electrical conductivity and high capacity.

[0044] In some embodiments, the pore volume of the porous carbon material is 0.6-1.2 cm 3 / g, for example, but not limited to, 0.6 cm3 / g, 0.7 cm 3 / g, 0.8 cm 3 / g, 0.9 cm 3 / g, 1 cm 3 / g or 1.2 cm 3 / g, etc., or a range value between any two of them. The porous carbon of the present disclosure has a suitable pore volume to ensure its mechanical strength and electrical performance, and the adsorption effect of the silicon material in the subsequent preparation of the silicon-carbon negative electrode material.

[0045] In some embodiments, the microporosity of the porous carbon material is 50% to 100%, which can be, but is not limited to, 50%, 60%, 70%, 80%, 85%, 90%, 95%, or 100%, etc., or a range value between any two of them. The porous carbon of the present disclosure has a large number of micropores, which is more conducive to ensuring the mechanical strength, adsorption performance, and electrical performance of the porous carbon.

[0046] In some specific embodiments of the present disclosure, the method for preparing the porous carbon material comprises the following steps:

[0047] (1) Microwave carbonization of the precursor

[0048] The carbonized material is obtained by microwave carbonization treatment of the alcohol-soluble lignin as the precursor under a humidified nitrogen atmosphere, and the temperature of the microwave carbonization treatment is 400-900°C.

[0049] (2) Chemical activation

[0050] The carbonized material obtained in step (1) is activated by potassium hydroxide (KOH) to obtain an activated material. The mass ratio of potassium hydroxide to carbonized material is 1:1 to 3:1, the activation treatment time is 0.5-4 h, and the activation treatment temperature is 600-900°C.

[0051] (3) The activated material obtained in step (2) is placed in a reducing atmosphere, and sequentially subjected to first heat treatment and second heat treatment. The temperature of the first heat treatment is 90-150°C, the holding time of the first heat treatment is 20-40 min, the temperature of the second heat treatment is 600-1000°C, and the holding time of the second heat treatment is 2-5 h, to obtain the porous carbon material.

[0052] In specific embodiments of the present disclosure, the method for preparing the porous carbon material is described by taking the above method for preparing the porous carbon material as an example.

[0053] In the above step (1), the humidified nitrogen atmosphere can effectively improve the pore-forming efficiency, and the microwave carbonization can form a large number of active centers. The carbonization treatment temperature includes, but is not limited to, 400°C, 500°C, 600°C, 700°C, 800°C, or 900°C, etc., or a range value between any two of them.

[0054] The mass ratio of the base and the carbonization material in step (2) above includes but is not limited to 1:1, 2:1, or 3:1, etc. The activation treatment time may be, for example but not limited to, 0.5 h, 1 h, 2 h, 3 h, or 4 h, etc., or a range value between any two of them. The activation treatment temperature may be, for example but not limited to, 600°C, 650°C, 700°C, 750°C, 800°C, or 900°C, etc., or a range value between any two of them.

[0055] The temperature of the first heat treatment in step (3) above may be, for example but not limited to, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., or a range value between any two of them; the holding time of the first heat treatment may be, for example but not limited to, 20 min, 25 min, 30 min, 40 min, etc., or a range value between any two of them. The temperature of the second heat treatment may be, for example but not limited to, 600°C, 700°C, 800°C, 900°C, 950°C, 1000°C, etc., or a range value between any two of them; the holding time of the second heat treatment may be, for example but not limited to, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, or 5 h, etc., or a range value between any two of them. The reducing atmosphere includes hydrogen.

[0056] The number and type of oxygen-containing functional groups on the surface of the porous carbon material are controlled by the activation treatment, and different activation processes will result in different surface functional groups. The present disclosure uses microwave carbonization, alkaline activation, and then reducing atmosphere passivation treatment on the porous carbon raw material to reduce or remove unstable surface functional groups (acidic functional groups), leaving a suitable amount of stable functional groups (neutral functional groups phenolic hydroxyl and basic functional groups carbonyl), thereby ensuring the electrical conductivity and wettability of the porous carbon, and ensuring the cycle performance and rate performance of the silicon-carbon negative electrode material prepared therefrom.

[0057] According to another aspect of the present disclosure, the present disclosure also relates to a silicon-carbon negative electrode material, comprising the porous carbon material and nano-silicon particles in the pores of the porous carbon material.

[0058] The silicon-carbon negative electrode material of the present disclosure has a suitable content of oxygen-containing surface functional groups, the rate of the silicon-carbon negative electrode material is significantly affected by the porous carbon, and the rate capability of the porous carbon depends on the influence of the oxygen-containing functional groups on the ion diffusion and electrical conductivity of the carbon material. Generally, the total content of the surface functional groups is inversely proportional to the electrical conductivity (the decrease in the electrical conductivity is due to the increase in defects, sp3carbon and impedance caused by the introduction of the oxygen-containing functional groups). However, if the content of the surface functional groups of the porous carbon is too low, the wettability of the porous carbon will be poor. In addition, the oxygen-containing functional groups on the surface of the porous carbon can increase the adsorption sites, and the concentration and distribution of the surface functional groups have a significant influence on the adsorption performance of the carbon material. The carbon material with a high content of oxygen-containing functional groups has a stronger adsorption force for polar gases, especially polar silicon-containing gases. The basic sites in the porous carbon material have a better chemical adsorption effect for silicon-containing gases. The phenolic hydroxyl functional group is a highly hydrophilic group that can interact with silicon-containing gas molecules through hydrogen bonding to promote adsorption and diffusion. It usually increases the polarity of the surface of the porous carbon material, thereby enhancing the interaction with silicon-containing gas molecules to improve the silicon utilization rate of the silicon-containing gas. In summary, to coordinate the electrical conductivity and wettability of the silicon-carbon negative electrode material, the content of the surface functional groups needs to be controlled within a suitable range.

[0059] In some embodiments, the mass content of the nanosilicon particles in the silicon-carbon negative electrode material is 5% to 85%, for example, 5%, 10%, 15%, 20%, 25%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, or any range between any two of them. The present disclosure loads a suitable content of silicon in the porous carbon material, thereby improving the electrical conductivity of the negative electrode material and increasing the capacity.

[0060] In some embodiments, the particle size Dv50 of the silicon-carbon negative electrode material is 3 to 10 μm, for example, but not limited to, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 10 μm, or any range between any two of them. The particle size Dv99 of the silicon-carbon negative electrode material is 10 to 25 μm, for example, but not limited to, 10 μm, 12 μm, 15 μm, 20 μm, 25 μm, or any range between any two of them. The particle size Dn10 of the silicon-carbon negative electrode material is 0.5 to 5 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm, or any range between any two of them. The silicon-carbon negative electrode material of the present disclosure has a suitable particle size. The small-particle material can be filled in the large-particle material, which helps to improve the compaction density of the electrode sheet, increase the volume energy density of the battery, and improve the charge-discharge performance and cycle performance.

[0061] In some embodiments, the specific surface area of the silicon-carbon negative electrode material is less than 3 m 2 / g, for example, but not limited to, 0.5 m 2 / g, 1 m2 / g, 1.5 m 2 / g, 1.8 m 2 / g, 2 m 2 / g, 2.5 m 2 / g or 2.8 m 2 / g, or a range value between any two of them. The silicon-carbon negative electrode material of the present disclosure has a suitable specific surface area, which is conducive to improving the electrical performance of the battery.

[0062] In some embodiments, the silicon-carbon negative electrode material has an electrical conductivity of 0.2-2 S / mm, for example, but not limited to, 0.2 S / mm, 0.5 S / mm, 0.8 S / mm, 1 S / mm, 1.5 S / mm, 2 S / mm, or a range value between any two of them. The silicon-carbon negative electrode material of the present disclosure has a high electrical conductivity by the cooperation of the porous carbon and the silicon material, which is more conducive to improving the electrical performance of the battery.

[0063] In some embodiments, 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 (such as LiF, etc.) and high molecular polymer. The present disclosure further coats the above-mentioned coating layer on the surface of the silicon-carbon negative electrode material, which can further improve the electrical performance of the silicon-carbon negative electrode material.

[0064] According to another aspect of the present disclosure, the present disclosure relates to a preparation method of a silicon-carbon negative electrode material, comprising the following steps:

[0065] The porous carbon material is subjected to vapor deposition in an atmosphere containing a silicon source to obtain the silicon-carbon negative electrode material.

[0066] The preparation method of the silicon-carbon negative electrode material of the present disclosure uses the above-mentioned specific porous carbon material, which can ensure the adsorption performance of the porous carbon to the silicon source gas molecules, improve the silicon utilization rate, improve the electrical conductivity, wettability and stability of the finally obtained silicon-carbon negative electrode material, improve the capacity and improve the cycle performance.

[0067] In some embodiments, the silicon source comprises a conventional silicon infiltration gas. The silicon source comprises at least one of monosilane (SiH4), disilane, trisilane, halosilane, polysilane, silole and its derivatives, silafluorene and its derivatives.

[0068] In some embodiments, the temperature for vapor deposition is 400-550℃, for example, but not limited to, 400℃, 450℃, 480℃, 500℃, 510℃, 550℃, or any range between any two of them. The holding time for vapor deposition is 3-5h, for example, but not limited to, 3h, 3.5h, 4h, 4.5h, or 5h, or any range between any two of them. The heating rate is 2-6℃ / min, for example, 2℃ / min, 5℃ / min, 6℃ / min, etc. The flow rate of the silicon source gas is 0.2-0.6L / min, for example, 0.2L / min, 0.3L / min, 0.4L / min, 0.5L / min, or 0.6L / min, or any range between any two of them. The atmosphere for vapor deposition is a protective gas, for example, nitrogen, helium, etc. The present disclosure uses appropriate vapor deposition conditions, thereby ensuring better deposition of the silicon source gas in the pores of the porous carbon, to obtain a silicon-carbon negative electrode material with high conductivity, high capacity, and high cycle performance.

[0069] In some embodiments, the method further comprises: performing a coating treatment on 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, fast ion conductor, and high molecular polymer. The coating treatment specifically comprises: after vapor deposition, performing a third heat treatment while continuously introducing a coating source gas. The present disclosure further performs surface coating on the silicon-carbon negative electrode material to improve the comprehensive performance of the final silicon-carbon negative electrode material.

[0070] In some embodiments, the temperature for the third heat treatment is 650-750℃, for example, but not limited to, 650℃, 680℃, 700℃, 720℃, 730℃, or 750℃, or any range between any two of them. The holding time for the third heat treatment is 2-4h, for example, but not limited to, 2h, 2.5h, 3h, 3.5h, or 4h, or any range between any two of them. The coating source gas comprises acetylene, methane, ethane, isopropane, propane, butane, isobutane, ethylene, butene, propylene, acetylene (C2H2), chloroethylene, chloroethane, fluoroethylene, pentachloro-fluoroethane, difluoroethane, 1,1-difluoroethylene, fluoromethane, chloromethane, difluoromethane, trifluoromethane, or LiF, etc. The heating rate for the third heat treatment is 2-6℃ / min, for example, 2℃ / min, 5℃ / min, 6℃ / min, etc. The third heat treatment is performed under a protective gas condition. The present disclosure uses appropriate third heat treatment conditions, thereby ensuring the coating effect, which is conducive to further improving the conductivity, capacity, and cycle performance of the silicon-carbon negative electrode material.

[0071] According to another aspect of the present disclosure, the present disclosure also relates to an electrode comprising the silicon-carbon negative electrode material.

[0072] The electrode of the present disclosure comprises a current collector and a negative electrode material layer on at least one side surface of the current collector, wherein the negative electrode material layer contains the above-mentioned silicon-carbon negative electrode material.

[0073] According to another aspect of the present disclosure, the present disclosure also relates to a lithium ion battery comprising the above-mentioned electrode.

[0074] The lithium ion battery of the present disclosure comprises the above-mentioned electrode, a positive electrode, a separator and an electrolyte. The battery of the present disclosure has excellent cycle performance, rate performance and safety performance.

[0075] According to another aspect of the present disclosure, the present disclosure also relates to an electrical equipment comprising the above-mentioned lithium ion battery.

[0076] The lithium ion battery of the present disclosure is applied to electrical equipment, which can ensure the power supply effect and improve the safety.

[0077] The present disclosure will be further explained and described in combination with specific examples and comparative examples.

[0078] Example 1

[0079] A preparation method of a silicon-carbon negative electrode material comprises the following steps:

[0080] (a) 1 kg of porous carbon material is placed in a rotary furnace, and then nitrogen protection is carried out, and then the temperature is raised to 450℃ at a rate of 5℃ / min, while the flow rate of silane is 0.5 L / min, and the duration of the inlet is 4 h, and the valve of the silicon source is closed.

[0081] The above-mentioned porous carbon has surface functional groups, which include basic functional groups and acidic functional groups. The basic functional groups include carbonyl and phenolic hydroxyl, and the acidic functional groups include hydroxyl and carboxyl. The content of carbonyl is 0.4 mmol / g, the content of phenolic hydroxyl is 0.2 mmol / g, and the content of carboxyl and hydroxyl is 0. The electrical conductivity of the porous carbon is 3.41 S / mm, the PH is 7.86, the particle size Dv50 of the porous carbon is 6.6 μm, the Dv99 is 16.2 μm, the Dn10 is 3.3 μm, the specific surface area is 1800 m 2 / g, and the pore volume is 0.82 cm 3 / g.

[0082] (b) Then the temperature is raised to 700℃ for the third heat treatment, and acetylene and argon are introduced, and the duration of the inlet is 3 h, to obtain a silicon-carbon negative electrode material with a mass content of silicon of 48%.

[0083] Example 2

[0084] A preparation method of a silicon-carbon negative electrode material comprises the following steps:

[0085] (a) 1 kg of the porous carbon material is placed in a rotary furnace, and then nitrogen is introduced for protection, and then the temperature is raised to 450℃ at a rate of 5℃ / min, while the flow rate of the introduced silane is 0.5 L / min, and the duration of the introduction is 4 h, and then the valve of the silane source is closed.

[0086] The porous carbon has surface functional groups, the surface functional groups include basic functional groups and acidic functional groups, the basic functional groups include carbonyl and phenolic hydroxyl, the acidic functional groups include hydroxyl and carboxyl, the content of the carbonyl is 0.5 mmol / g, the content of the phenolic hydroxyl is 0.2 mmol / g, and the content of the carboxyl and the hydroxyl is 0. The conductivity of the porous carbon is 3.34 S / mm, and the PH is 7.30; the particle size Dv50 of the porous carbon is 8.5 μm, the Dv99 is 14.5 μm, the Dn10 is 3.5 μm, the specific surface area is 2100 m 2 / g, and the pore volume is 0.88 cm 3 / g.

[0087] (b) Then the third heat treatment is performed by raising the temperature to 700℃, and acetylene and argon are introduced, the duration of the introduction is 3 h, and a silicon-carbon negative electrode material with a mass content of silicon of 50% is obtained.

[0088] Example 3

[0089] The difference between the preparation method of the silicon-carbon negative electrode material and that of Example 1 is that:

[0090] In the porous carbon, the content of the carbonyl is 0.5 mmol / g, the content of the phenolic hydroxyl is 0.4 mmol / g, and the content of the carboxyl and the hydroxyl is 0.08 mmol / g. The conductivity of the porous carbon is 2.98 S / mm, and the PH is 7.81; the particle size Dv50 of the porous carbon is 10 μm, the Dv99 is 17.5 μm, the Dn10 is 2.8 μm, the specific surface area is 2090 m 2 / g, and the pore volume is 0.95 cm 3 / g.

[0091] In the obtained silicon-carbon negative electrode material, the mass content of silicon is 51%.

[0092] Example 4

[0093] The difference between the preparation method of the silicon-carbon negative electrode material and that of Example 1 is that:

[0094] In the porous carbon, the content of the carbonyl is 0.45%, the content of the phenolic hydroxyl is 0.3 mmol / g, and the content of the carboxyl and the hydroxyl is 0.18 mmol / g. The conductivity of the porous carbon is 2.91 S / mm, and the PH is 7.37; the particle size Dv50 of the porous carbon is 5.1 μm, the Dv99 is 10.2 μm, the Dn10 is 1.2 μm, the specific surface area is 1937 m 2 / g, and the pore volume is 0.86 cm3 / g.

[0095] The obtained silicon-carbon negative electrode material has a silicon mass content of 46.6%.

[0096] Example 5

[0097] A method for preparing a silicon-carbon negative electrode material includes the following steps:

[0098] (a) 1 kg of porous carbon material is placed in a rotary furnace, and then nitrogen protection is introduced, and then the temperature is raised to 550 DEG C at a rate of 6 DEG C / min, while the flow rate of 0.6 L / min of silane is introduced, and the introduction time is 3 h, and the valve of the silicon source is closed. The porous carbon is the same as in Example 1.

[0099] (b) Then the temperature is raised to 750 DEG C for the third heat treatment, and acetylene and argon are introduced, and the introduction time is 2 h, and the silicon mass content of the obtained silicon-carbon negative electrode material is 47%.

[0100] Example 6

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

[0102] (a) 1 kg of porous carbon material is placed in a rotary furnace, and then nitrogen protection is introduced, and then the temperature is raised to 550 DEG C at a rate of 6 DEG C / min, while the flow rate of 0.6 L / min of silane is introduced, and the introduction time is 3 h, and the valve of the silicon source is closed. The porous carbon is the same as in Example 1.

[0103] (b) Then the temperature is raised to 750 DEG C for the third heat treatment, and acetylene and argon are introduced, and the introduction time is 2 h, and the silicon mass content of the obtained silicon-carbon negative electrode material is 47%.

[0104] Comparative Example 1

[0105] A method for preparing a silicon-carbon negative electrode material, which is different from Example 1 in that:

[0106] The surface functional groups of the porous carbon include a carbonyl content of 1.2 mmol / g, a phenolic hydroxyl content of 0.6 mmol / g, and a content of carboxyl and hydroxyl each independently of 0.5 mmol / g. The electrical conductivity of the porous carbon is 0.02 S / mm, and the pH is 8.94; the particle size Dv50 of the porous carbon is 8.2 μm, the Dv99 is 15.5 μm, the Dn10 is 3.0 μm, the specific surface area is 1900 m 2 / g, and the pore volume is 0.73 cm 3 / g.

[0107] Comparative Example 2

[0108] A method for preparing a silicon-carbon negative electrode material, which is different from Example 1 in that:

[0109] The surface functional groups of the porous carbon include carbonyl groups, phenolic hydroxyl groups, and carboxyl and hydroxyl groups, wherein the content of the carbonyl groups is 0.1 mmol / g, the content of the phenolic hydroxyl groups is 0.1 mmol / g, and the content of the carboxyl and hydroxyl groups is 0. The conductivity of the porous carbon is 1.13 S / mm, and the pH is 7.51. The particle size Dv50 of the porous carbon is 8.8 μm, the particle size Dv99 is 18.5 μm, the particle size Dn10 is 3.6 μm, the specific surface area is 2020 m 2 / g, and the pore volume is 0.83 cm 3 / g.

[0110] Experimental Example

[0111] I. Performance test of the silicon-carbon negative electrode material

[0112] The silicon-carbon negative electrode material obtained in the examples and comparative examples was tested for conductivity, pH, and silane utilization rate, and the test results are shown in Table 1.

[0113] The test method of the surface functional groups is as follows: according to the national standard GBT-38114-2019, the acid-base titration method of Boehm is used for determination.

[0114] The principle is as follows: in the aqueous solutions of the four alkalis of NaHCO3, Na2CO3, NaOH and CH3CH2ONa, the basicity increases in turn, NaHCO3 can only neutralize the functional groups (I type functional groups) on the surface of the activated carbon with relatively strong acidity such as carboxyl groups; Na2CO3 can neutralize the functional groups on the surface of the activated carbon with carboxyl groups and hydroxyl groups in lactone form (I+II type functional groups); NaOH can neutralize the functional groups on the surface of the activated carbon with carboxyl groups, hydroxyl groups in lactone form and phenolic hydroxyl groups (I+II+III type functional groups); CH3CH2ONa has the strongest basicity and can neutralize most of the functional groups on the surface of the activated carbon (I+II+III+IV type functional groups). Then, the consumption amount of CH3CH2ONa for neutralizing the acidic surface functional groups is subtracted from the consumption amount of NaOH for neutralizing the acidic surface functional groups, so that the content of the IV type functional groups can be calculated, and the contents of the III, II and I type functional groups can be calculated in turn, and the unit is mmol / g.

[0115] The test method of the conductivity is as follows: a resistivity tester (Ningbo Ruikai FT-301B automatic conductor powder resistivity tester) is used, the negative electrode is taken, the electronic press is used for constant voltage to 5000 kg±2 kg, and maintained for 15 s to 25 s, the sample is placed between the electrodes of the tester, the sample height h (cm), the voltage U between the two ends, the current I, the resistance R (KΩ), and the area S of the powder after pressing = 3.14 cm 2 , according to the formula δ = h / (S×R) / 1000, the electronic conductivity of the powder is calculated, and the unit is S / mm.

[0116] Method for testing utilization rate of silane: utilization rate of silane (%) = [amount of collected material (g) x silicon content (%)] / [volume of silane (L) x density of silane (g / L)].

[0117] Method for testing silicon content: the silicon content is calculated by using the weight of oxygen after the carbon is completely oxidized and the silicon is completely converted into silicon dioxide by using a thermogravimetric analyzer at 1000℃ in air for 1h. The specific process is as follows:

[0118] (1) about 2g of the silicon-carbon material is weighed, and the actual mass is recorded as m0; and the crucible with a mass of m1 is placed.

[0119] (2) the crucible is placed in a tube furnace or a muffle furnace, compressed air is continuously supplied, the temperature is increased to 600℃ at a rate of 10℃ / min, and the temperature is kept for 1h, and then the temperature is increased to 1000℃ at the same rate and kept for 1h.

[0120] (3) after natural cooling to room temperature, the crucible is taken out, and the mass is weighed as m2.

[0121] (4) the silicon content (%) = (m2-m0) x MSi / MSiO2 / m1 x 100% is calculated.

[0122] Wherein, MSiO2 is the relative molecular mass of SiO2, 60.084g / mol; and MSi is the relative molecular mass of Si, 28.0855g / mol.

[0123] Table 1: test results of the silicon-carbon negative electrode material

[0124] As shown in Table 1, the porous carbon with a suitable content of functional groups is used to prepare the silicon-carbon negative electrode material, and the obtained silicon-carbon negative electrode material has high electrical conductivity, suitable pH, high silane utilization rate, and better electrical performance of the silicon-carbon negative electrode material.

[0125] In the porous carbon of Comparative Example 1, the contents of carbonyl, phenolic hydroxyl, hydroxyl and carboxyl are all too high, that is, the total content of the surface functional groups of the porous carbon is too high, the electrical conductivity of the obtained silicon-carbon negative electrode material is low, the pH is too high, and the silane utilization rate is low. In the porous carbon of Comparative Example 2, the contents of carbonyl and phenolic hydroxyl are both too low, that is, the total content of the surface functional groups of the porous carbon is too low, the electrical conductivity of the obtained silicon-carbon negative electrode material is low, and the silane utilization rate is low.

[0126] II. Test of electrical performance of the battery

[0127] The silicon-carbon negative electrode materials obtained in each example and comparative example are used to prepare batteries, and the preparation method of the battery comprises:

[0128] Silicon-carbon negative electrode material (negative electrode active material), polyacrylic acid resin (PAA), single carbon nanotube (CNT) and conductive carbon black (SP) were mixed in a mass ratio of 82:7:1:10, and deionized water was used to prepare a slurry, which was uniformly coated on a copper foil, vacuum dried at 80°C for 24h, to obtain the experimental battery electrode; lithium sheet was used as the counter electrode; 1.1 mol / L LiPF6 electrolyte was used, the solvent was a four-component mixed solvent, ethylene carbonate (EC): vinylene carbonate (VC): dimethyl carbonate (DMC): fluoroethylene carbonate (FEC) = 1:1:1:1 (mass ratio); polypropylene microporous film was used as the separator; and a CR2025 type button half-battery was assembled in a vacuum glove box.

[0129] The rate performance and cycle performance were tested by using a battery test system (half-battery test American Arbin multi-channel battery test system, German Braun Labstar (1200 / 780) type glove box).

[0130] Rate performance test: under normal temperature conditions, 0.1C current was cycled for 5 weeks, then 0.2C current was cycled for 5 weeks, 0.5C current was cycled for 5 weeks, 1C current was cycled for 5 weeks, 2C current was cycled for 5 weeks, and finally 0.1C current was cycled for 5 weeks.

[0131] Cycle performance test: under normal temperature conditions, 1C constant current charging and discharging was performed to 0.01V, then 0.05C constant current discharging was performed to 0.005V, and finally 1C constant current charging was performed to 1.5V to obtain the delithiation specific capacity, which was cycled for 300 times, and the capacity retention rate of 300 cycles was calculated. The 300 cycle capacity retention rate was the ratio of the delithiation specific capacity of the 300th week to the delithiation specific capacity of the 1st week.

[0132] The results of the electrical performance test of the battery are shown in Table 2.

[0133] Table 2: Results of the electrical performance test of the battery

[0134] As can be seen from Table 2, the silicon-carbon negative electrode material prepared by using the porous carbon with appropriate types and contents of functional groups, and further prepared into a battery, has excellent cycle performance and rate performance, and the capacity retention rate is above 90%, and the cycle number of 80% capacity retention rate is above 50 weeks.

[0135] The surface functional group content of the porous carbon of Comparative Example 1 is too high, which hinders ion diffusion, and reduces the cycle performance and rate performance of the obtained battery. The surface functional group content of the porous carbon of Comparative Example 2 is too low, the wettability of the material is poor, the utilization rate of the silicon material is low, and the cycle performance and rate performance of the battery are reduced.

[0136] Compared with the prior art, the present disclosure has the following beneficial effects:

[0137] (1) The present disclosure controls the surface of the porous carbon material to have a suitable content and type of functional groups, thereby ensuring high conductivity, wettability and stability of the porous carbon.

[0138] (2) The silicon-carbon negative electrode material of the present disclosure, the combination of porous carbon and nano-silicon particles, can ensure high conductivity, high capacity and high cycle performance.

[0139] (3) The preparation method of the silicon-carbon negative electrode material of the present disclosure uses a specific porous carbon material, which is beneficial to the adsorption effect of the porous carbon on the silicon-containing gas, can improve the silicon utilization rate of the silicon-containing gas, and makes the finally obtained silicon-carbon negative electrode material have high conductivity and suitable wettability, improves its capacity, and improves its cycle performance.

[0140] (4) The lithium ion battery obtained from the silicon-carbon negative electrode material of the present disclosure has excellent cycle performance, rate performance and safety performance.

[0141] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the present disclosure, and not to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present disclosure. Industrial applicability

[0142] The porous carbon material of the present disclosure controls the surface of the porous carbon material to have a suitable content and type of functional groups, thereby ensuring high conductivity, wettability and stability of the porous carbon; the silicon-carbon negative electrode material of the present disclosure, the combination of porous carbon and nano-silicon particles, can ensure high conductivity, high capacity and high cycle performance; the preparation method of the silicon-carbon negative electrode material of the present disclosure uses a specific porous carbon material, which is beneficial to the adsorption effect of the porous carbon on the silicon-containing gas, can improve the silicon utilization rate of the silicon-containing gas, and makes the finally obtained silicon-carbon negative electrode material have high conductivity and suitable wettability, improves its capacity, and improves its cycle performance; the lithium ion battery obtained from the silicon-carbon negative electrode material of the present disclosure has excellent cycle performance, rate performance and safety performance; the lithium ion battery of the present disclosure is applied to an electric device, which can ensure the power supply effect and improve the safety.

Claims

1. A porous carbon material, characterized by, The porous carbon material has surface functional groups, and the surface functional groups include basic functional groups, neutral functional groups, and acidic functional groups. The content of the surface functional groups is 0.4-1 mmol / g, wherein the content of the basic functional groups is 0.2-0.5 mmol / g, the content of the neutral functional groups is 0.2-0.4 mmol / g, and the content of the acidic functional groups is less than 0.2 mmol / g.

2. The porous carbon material according to claim 1, characterized in that, At least one of the following features (1) and (2) is included: (1) The content of the surface functional groups is 0.4-0.7 mmol / g, wherein the content of the basic functional groups is 0.2-0.5 mmol / g, the content of the neutral functional groups is 0.2-0.4 mmol / g, and the content of the acidic functional groups is less than 0.1 mmol / g; (2) The basic functional groups include carbonyl groups, the neutral functional groups include phenolic hydroxyl groups, and the acidic functional groups include hydroxyl groups and / or carboxyl groups.

3. The porous carbon material according to any one of claims 1 to 2, characterized in that, At least one of the following features (1) to (7) is included: (1) The electrical conductivity of the porous carbon material is 2-5 S / mm; (2) The pH of the porous carbon material is 6.8-8; (3) The particle size Dv50 of the porous carbon material is 3-10 μm; (4) The particle size Dv99 of the porous carbon material is 10-25 μm, and the particle size Dn10 of the porous carbon material is 0.5-5 μm; (5) the specific surface area of the porous carbon material is 1000-2200 m 2 / g; (6) the porous carbon material has a pore volume of 0.6 to 1.2 cm 3 / g; (7) The microporosity of the porous carbon material is 50%-100%.

4. A silicon-carbon negative electrode material, characterized by, The porous carbon material according to any one of claims 1-3 and nano-silicon particles in the pores of the porous carbon material.

5. The silicon-carbon negative electrode material of claim 4, wherein, At least one of the following features (1) to (5) is included: (1) In the silicon-carbon negative electrode material, the mass content of the nano-silicon particles is 5%-85%; (2) 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; (3) the silicon-carbon negative electrode material has a specific surface area of less than 3 m 2 / g; (4) The electrical conductivity of the silicon-carbon negative electrode material is 0.2-2 S / mm; (5) The surface of the silicon-carbon negative electrode material further includes a coating layer, and the coating layer includes at least one of amorphous carbon, fast ion conductor, and high polymer.

6. The method of producing a silicon-carbon negative electrode material according to claim 4 or 5, characterized in that, The following steps are included: The porous carbon material is subjected to vapor deposition in an atmosphere containing a silicon source to obtain the silicon-carbon negative electrode material.

7. The method of producing a silicon-carbon negative electrode material according to claim 6, characterized by, Further including: 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, and the coating layer includes at least one of amorphous carbon, fast ion conductor, and high polymer.

8. An electrode characterized by, The silicon-carbon negative electrode material according to claim 4 or 5 is included.

9. A lithium-ion battery, characterized by The electrode according to claim 8 is included.

10. An electric device, characterized by The lithium ion battery according to claim 9 is included.

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