Porous carbon materials and their preparation methods, and silicon-carbon anode active materials and their applications

Abstract

This application discloses a method for preparing porous carbon materials, comprising the following steps: a. mixing a hard carbon resin precursor and a soft carbon resin precursor to obtain a resin precursor material; b. mixing the resin precursor material obtained in step a with an alkaline activator, performing activation treatment, washing, and drying to obtain a porous carbon material precursor; c. placing the porous carbon material precursor obtained in step b in an inert atmosphere and performing heat treatment at 1300-2000℃ to obtain a porous carbon material. The porous carbon material of this application exhibits excellent electron transport performance. The silicon-carbon anode active material prepared by depositing silicon using this porous carbon material has excellent conductivity, effectively reducing the powder resistance of the anode material while imparting high capacity and high first-efficiency.

Description

Technical Field

[0001] This application belongs to the field of secondary battery technology, specifically relating to a porous carbon material and its preparation method. Furthermore, this application also relates to a silicon-carbon anode active material. In particular, this application also relates to a secondary battery and an electrical device. Background Technology

[0002] The novel silicon-carbon product is a new type of anode active material prepared by silicon deposition using porous carbon as a substrate. It is mainly used in lithium-ion battery anode materials. Compared with traditional carbon-based anode materials, it benefits from the "confining" effect of porous carbon and a higher silicon content. Compared with traditional silicon-carbon and silicon-oxygen anodes, it has higher capacity and first-time efficiency, and has broad application prospects.

[0003] Currently, novel silicon-carbon materials, especially ultra-high capacity novel silicon-carbon materials with a charging capacity of more than 2000mAh / g at 0.8V, are facing challenges in applications such as low-altitude aircraft. Due to the demand for ultra-high capacity in these applications, the high silicon loading in the porous carbon leads to unstable material structure and high powder resistivity, which severely limits the application of ultra-high capacity novel silicon-carbon materials in this field.

[0004] Therefore, it is necessary to conduct in-depth research on silicon-carbon anode materials in order to improve the capacity of this type of material while improving its conductivity, thereby realizing the large-scale promotion of ultra-high capacity novel silicon-carbon materials. Summary of the Invention

[0005] This application aims to at least partially solve one of the technical problems in the related art. To this end, embodiments of this application propose a porous carbon material and a method for preparing the same. By mixing a hard carbon resin precursor and a soft carbon resin precursor to obtain a soft and hard carbon resin precursor, a porous carbon material combining soft and hard carbon is obtained. The silicon-carbon anode active material prepared by depositing silicon using this porous carbon material has excellent conductivity, and while imparting high capacity and high first-efficiency to the anode material, it effectively reduces the powder resistance of the anode material.

[0006] This application provides a method for preparing porous carbon materials, including the following steps:

[0007] a. Mix hard carbon resin precursor and soft carbon resin precursor to obtain resin precursor material;

[0008] b. Mix the resin precursor material obtained in step a with an alkaline activator, perform activation treatment, and then wash and dry to obtain a porous carbon material precursor.

[0009] c. The porous carbon material precursor obtained in step b is placed in an inert atmosphere and heat-treated at 1300-2000℃ to obtain porous carbon material.

[0010] The advantages and technical effects of the silicon-carbon anode active material in this application embodiment are as follows:

[0011] In the method of this application embodiment, during the preparation of the resin precursor, a soft carbon resin precursor is added to a hard carbon resin precursor, and a porous carbon precursor material combining soft and hard carbon is prepared by an alkali-activated template method. Finally, the soft carbon portion in the porous carbon precursor material is graphitized by high-temperature heat treatment. The resulting porous carbon material has excellent electron transport performance, which makes the silicon-carbon anode active material prepared by silicon deposition using this porous carbon material have excellent conductivity. While giving the anode material high capacity and high first-efficiency, it effectively reduces the powder resistance of the anode material.

[0012] In some embodiments, in step a, the hard carbon resin precursor includes phenolic resin. Preferably, the raw materials for preparing the hard carbon resin precursor include phenol and formaldehyde. More preferably, the molar ratio of phenol to formaldehyde is 2-4:1.

[0013] In some embodiments, in step a, the soft carbon resin precursor includes at least one of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), or polyethylene (PE).

[0014] In some embodiments, in step a, the mass ratio of the hard carbon resin precursor to the soft carbon resin precursor is 1-2:1.

[0015] In some embodiments, in step b, the alkaline activator includes potassium hydroxide.

[0016] In some embodiments, in step b, the mass ratio of carbon to alkaline activator in the resin precursor material is 1:(2-8).

[0017] In some embodiments, in step b, the activation treatment is carried out under an inert atmosphere, the activation temperature is 700-900℃, and the activation time is 3-8h.

[0018] In some embodiments, in step b, the washing process involves sequentially washing with hydrochloric acid and deionized water until the solution is neutral.

[0019] In some embodiments, in step c, the inert atmosphere uses at least one of nitrogen or argon.

[0020] In some embodiments, the heat treatment time in step c is 2-4 hours.

[0021] This application also provides a porous carbon material prepared using the method described in this application.

[0022] The porous carbon material in this application embodiment is a porous carbon-based material that combines hard carbon and soft carbon, possessing the advantages of both. It is not only structurally stable but also has excellent electron transport performance, enabling the silicon-carbon anode active material prepared by depositing silicon using this porous carbon material to have excellent conductivity. While giving the anode material high capacity and high first-efficiency, it effectively reduces the powder resistance of the anode material.

[0023] This application also provides a silicon-carbon anode active material, which includes a porous carbon material and silicon distributed within the porous carbon material. The porous carbon material is either a porous carbon material prepared by the method of this application embodiment or a porous carbon material of this application embodiment.

[0024] The silicon-carbon anode active material of this application embodiment not only has high capacity and high initial efficiency, but also excellent conductivity, and can control the powder resistivity to below 20Ω*cm.

[0025] This application also provides a method for preparing a silicon-carbon anode active material, including the following steps:

[0026] (1). Using porous carbon material as raw material, silicon source is introduced under inert protective gas to perform silicon deposition and obtain silicon-carbon core;

[0027] (2). The material obtained after silicon deposition in step a is subjected to carbon coating treatment to obtain silicon-carbon anode active material.

[0028] In the preparation method of silicon-carbon anode active material in the embodiments of this application, the porous carbon material combining soft and hard carbon of this application is used as the carbon substrate, which enables the silicon-carbon anode active material to maintain excellent conductivity while having high capacity and high first-time efficiency, and effectively reduces the powder resistance of the anode material.

[0029] In some embodiments, in step (1), the silicon source includes at least one of silane or ethyl silane.

[0030] In some embodiments, in step (1), the mass ratio of the silicon source to the porous carbon material is (1.5-2):1.

[0031] In some embodiments, in step (1), the inert protective gas includes at least one of nitrogen or argon.

[0032] In some embodiments, in step (1), the silicon source is introduced at a rate of 1-5 L / min.

[0033] In some embodiments, in step (1), the silicon deposition temperature is 480℃-580℃ and the time is 5-10h.

[0034] In some embodiments, in step (2), acetylene is used for carbon coating treatment. Preferably, the acetylene injection rate is 1-5 L / min, the carbon coating treatment temperature is 550-600℃, and the carbon coating treatment time is 1-5 h.

[0035] This application also provides a secondary battery, including the silicon-carbon anode active material of this application embodiment or the silicon-carbon anode active material prepared by the method of this application embodiment. The secondary battery of this application embodiment possesses all the advantages of the silicon-carbon anode active material of this application embodiment, which will not be repeated here.

[0036] This application also provides an electrical device, including a secondary battery as described in this application embodiment. The electrical device of this application embodiment possesses all the advantages of the secondary battery of this application embodiment, which will not be elaborated further here. Attached Figure Description

[0037] Figure 1 The images show the XRD patterns of the porous carbon materials prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0038] The embodiments of this application are described in detail below. These embodiments are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0040] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0041] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0042] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0044] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0045] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0046] This application provides a method for preparing porous carbon materials, including the following steps:

[0047] a. Mix hard carbon resin precursor and soft carbon resin precursor to obtain resin precursor material;

[0048] b. Mix the resin precursor material obtained in step a with an alkaline activator, perform activation treatment, and then wash and dry to obtain a porous carbon material precursor.

[0049] c. The porous carbon material precursor obtained in step b is placed in an inert atmosphere and heat-treated at 1300-2000℃ to obtain porous carbon material.

[0050] In the method of this application embodiment, the heat treatment temperature is controlled to be 1300-2000℃, preferably 1300-1800℃, such as 1300℃, 1400℃, 1500℃, 1600℃, 1700℃, 1800℃, etc. If the heat treatment temperature is too high, it will affect the pore structure of the porous carbon material, resulting in a reduction in the total pore volume. In severe cases, it will cause a large number of closed pores to be unable to deposit silicon. If the heat treatment temperature is too low, it will be detrimental to the graphitization of soft carbon and will not be conducive to improving the electron transport performance of the porous carbon material.

[0051] The method of this application addresses the problem of unstable structure in current high-capacity silicon-carbon anode materials. During the preparation of the resin precursor for porous carbon materials, a soft carbon resin precursor is added to the hard carbon resin precursor. An alkaline activation template method is used to prepare a porous carbon precursor material combining hard and soft carbon. Finally, the soft carbon portion of the porous carbon precursor material is graphitized through high-temperature heat treatment. The resulting porous carbon material exhibits excellent electron transport performance, enabling the silicon-carbon anode active material prepared by silicon deposition using this porous carbon material to possess excellent conductivity. While imparting high capacity and high initial efficiency to the anode material, this method effectively reduces the powder resistance of the anode material.

[0052] In some embodiments, in step a, the hard carbon resin precursor includes phenolic resin. Preferably, the raw materials for preparing the hard carbon resin precursor include phenol and formaldehyde. More preferably, the molar ratio of phenol to formaldehyde is 2-4:1. In this embodiment, phenolic resin, a hard carbon resin precursor, is prepared using phenol and formaldehyde as raw materials, providing a hard carbon structural portion for porous carbon materials, which is beneficial for obtaining structurally stable porous carbon materials.

[0053] In some embodiments, in step a, the soft carbon resin precursor includes at least one of polyvinylpyrrolidone, polyethylene glycol, or polyethylene, preferably polyvinylpyrrolidone. In this application embodiment, introducing a soft carbon resin precursor into a hard carbon resin precursor yields a resin precursor material combining soft and hard carbon, enabling the porous carbon material to not only maintain a stable structure but also improve its electron transport performance.

[0054] In some embodiments, in step a, the mass ratio of the hard carbon resin precursor to the soft carbon resin precursor is 1-2:1. In this application embodiment, the preferred ratio of hard carbon to soft carbon resin precursors is beneficial for improving the electron transport performance of the material while maintaining material structural stability, thereby increasing the capacity and conductivity of the silicon-carbon anode active material and reducing powder resistivity. If too much soft carbon resin precursor material is added, it will be detrimental to increasing the silicon deposition amount and the capacity of the anode active material; if too little soft carbon resin precursor material is added, it will be detrimental to improving conductivity and reducing the powder resistivity of the silicon-carbon anode material.

[0055] In some embodiments, in step b, the alkaline activator includes potassium hydroxide; the mass ratio of carbon to alkaline activator in the resin precursor material is 1:(2-8). The activation treatment is carried out under an inert atmosphere at a temperature of 700-900℃ for 3-8 hours, and the washing is performed sequentially with hydrochloric acid and deionized water until neutral. In this embodiment, the resin precursor material is activated with an alkaline activator. During the activation process, the carbon consumed mainly generates potassium carbonate. The potassium vapor reduced by carbon at high temperature continuously enters the spaces between the carbon atoms to activate the porous carbon material precursor.

[0056] In some embodiments, in step c, the inert atmosphere uses at least one of nitrogen or argon.

[0057] In some embodiments, the heat treatment time in step c is 2-4 hours. In this application embodiment, a preferred heat treatment time is beneficial for the graphitization of the porous carbon material precursor. If the heat treatment time is too long, it will hinder the increase of the total pore volume of the porous carbon material and may even cause a large number of closed pores. If the heat treatment time is too short, it will hinder the composite of soft and hard carbons in the porous carbon material, which is detrimental to improving electron transport performance and thus hinders the reduction of the powder resistivity of the silicon-carbon anode active material.

[0058] This application also provides a porous carbon material, prepared using the method described in this application. The porous carbon material of this application is a porous carbon-based material combining hard and soft carbon, possessing the advantages of both. It not only has a stable structure but also excellent electron transport properties, enabling the silicon-carbon anode active material prepared by depositing silicon using this porous carbon material to exhibit excellent conductivity. While imparting high capacity and high initial efficiency to the anode material, it effectively reduces the powder resistance of the anode material.

[0059] This application also provides a silicon-carbon anode active material, which includes a porous carbon material and silicon distributed within the porous carbon material. The porous carbon material is either the porous carbon material prepared by the method of this application embodiment or the porous carbon material of this application embodiment. The silicon-carbon anode active material of this application embodiment not only has high capacity and high initial efficiency, but also excellent conductivity, capable of controlling the powder resistivity below 20 Ω*cm.

[0060] This application also provides a method for preparing a silicon-carbon anode active material, including the following steps:

[0061] (1). Using porous carbon material as raw material, silicon source is introduced under inert protective gas to perform silicon deposition and obtain silicon-carbon core;

[0062] (2). The material obtained after silicon deposition in step a is subjected to carbon coating treatment to obtain silicon-carbon anode active material.

[0063] In the preparation method of silicon-carbon anode active material in the embodiments of this application, the porous carbon material combining soft and hard carbon of this application is used as the carbon substrate, which enables the silicon-carbon anode active material to maintain excellent conductivity while having high capacity and high first-time efficiency, and effectively reduces the powder resistance of the anode material.

[0064] In some embodiments, in step (1), the silicon source includes at least one of silane or silane; preferably, the mass ratio of the silicon source to the porous carbon material is (1.5-2):1; the silicon source is introduced at a rate of 1-5 L / min; the inert protective gas includes at least one of nitrogen or argon; in the silicon deposition, the silicon deposition temperature is 480℃-580℃, and the time is 5-10 h. In this application embodiment, there are no particular limitations on the silicon source and silicon deposition process; the silicon source and silicon deposition process used in the prior art are applicable to this application.

[0065] In some embodiments, in step (2), acetylene is used for carbon coating treatment. Preferably, the acetylene injection rate is 1-5 L / min, the carbon coating treatment temperature is 550-600℃, and the carbon coating treatment time is 1-5 h.

[0066] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0067] Example 1

[0068] I. Preparation of porous carbon materials

[0069] Preparation of precursor: Phenol (chemically pure) and formaldehyde solution (chemically pure, density approximately 1.1 g / cm³) were mixed. 3 A mixture of phenol and pure ammonia (36-38 wt%) was prepared at a mass ratio of 3:1. Then, concentrated ammonia (chemically pure, 25-28 wt%) was added at a mass ratio of 1:1. After thorough mixing, a mixed solution was obtained. Polyvinylpyrrolidone (PVP, K90) powder, a precursor for soft carbon resin, was added to the mixed solution. The mixture was heated in a boiling water bath until it separated into two layers. When the viscosity of the bottom layer of resin increased, it was removed and cooled to obtain a yellow resin, which is the precursor for the combined soft and hard carbon resin. The mass ratio of the hard carbon resin precursor phenolic resin to the soft carbon resin precursor PVP was 1.5:1.

[0070] Alkali activation treatment: The soft and hard carbon-bonded resin precursor is mixed with KOH, wherein the mass ratio of carbon to KOH in the soft and hard carbon-bonded resin precursor is 1:5. Under a nitrogen atmosphere, it is first dehydrated and cured at 500℃ for 3 hours, and then calcined at about 800℃ for 5 hours. After cooling, the product is thoroughly washed with 0.1mol / L hydrochloric acid and deionized water until neutral, and then dried to obtain a soft and hard carbon-bonded porous carbon material precursor.

[0071] Heat treatment: The porous carbon material precursor combining soft and hard carbon is heat treated at 1500℃ for 3 hours to obtain porous carbon material.

[0072] II. Preparation of silicon-carbon anode active materials

[0073] Silicon deposition: The porous carbon material prepared above is placed in a fluidized bed reactor with argon as the protective atmosphere. Silane gas is introduced at a rate of 3 L / min at 500 °C. The mass ratio of silane introduced to porous carbon material is 1.5. Silicon deposition is carried out for 7 h. After silicon deposition is completed, a silicon-carbon core is obtained.

[0074] Carbon coating: After silicon deposition, acetylene is introduced at a rate of 3 L / min, and deposition is carried out at 550 °C for 2 h to complete carbon coating and obtain silicon-carbon anode active material.

[0075] Example 2

[0076] The method is the same as in Example 1, except that the heat treatment temperature is 1800°C during the preparation of the porous carbon material.

[0077] Example 3

[0078] The method is the same as in Example 1, except that the heat treatment temperature is 1300°C during the preparation of the porous carbon material.

[0079] Example 4

[0080] The method is the same as in Example 1, except that the soft carbon resin precursor added during the preparation of porous carbon materials is polyethylene glycol.

[0081] Example 5

[0082] The method is the same as in Example 1, except that the soft carbon resin precursor added during the preparation of porous carbon materials is polyethylene.

[0083] Example 6

[0084] The method is the same as in Example 1, except that the mass ratio of hard carbon resin precursor to soft carbon resin precursor PVP is 2:1 during the preparation of porous carbon materials.

[0085] Example 7

[0086] The method is the same as in Example 1, except that the mass ratio of hard carbon resin precursor to soft carbon resin precursor PVP is 1:1 during the preparation of porous carbon materials.

[0087] Comparative Example 1

[0088] The method is the same as in Example 1, except that heat treatment is omitted in the preparation of porous carbon materials, and the carbon material after alkali activation treatment and washing and drying is used as porous carbon material.

[0089] Comparative Example 2

[0090] The method is the same as in Example 1, except that PVP is not added during the preparation of the resin precursor in the process of preparing porous carbon materials, and the heat treatment is eliminated.

[0091] Comparative Example 3

[0092] The method is the same as in Example 1, except that the heat treatment temperature is 1100°C during the preparation of the porous carbon material.

[0093] Comparative Example 4

[0094] The method is the same as in Example 1, except that the heat treatment temperature is 2200°C during the preparation of porous carbon materials.

[0095] The porous carbon materials and silicon-carbon anode active materials prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to performance tests. The test results are shown in the figure. Figure 1 Tables 1 and 2.

[0096] 1. The pore volume and pore size of porous carbon materials were tested using a specific surface area analyzer, and the test method was GB / T19077-2016;

[0097] 2. Battery assembly: A negative electrode slurry is prepared by mixing silicon-carbon negative electrode active material, binder, and conductive agent in a mass ratio of 8:1:1. The negative electrode slurry is coated on the surface of nickel foam and dried to obtain a negative electrode sheet. The negative electrode sheet, positive electrode sheet (active material is ternary NCM523), electrolyte (electrolyte is 1M lithium hexafluorophosphate, solvent is EC:DMC (volume ratio) = 1:1), and separator (PE membrane) are assembled into a button cell.

[0098] Test conditions: ① Discharge: 0.1C-0.0005V, discharge specific capacity is denoted as Q1, Q1 is the initial discharge specific capacity; ② Charge: 0.1C-0.8V, charge specific capacity is denoted as Q2; Q2 is the initial charge specific capacity; coin charge first efficiency is abbreviated as ICE, ICE = Q2 / Q1; the capacity retention rate is tested after 100 cycles at 0.1C to reflect the material's cycle performance and structural damage.

[0099] Powder resistivity: Powder resistivity is tested using the four-probe method (GB / T 39978-2021). Powder resistivity reflects the conductivity of the material. The lower the resistivity, the better the conductivity, which is beneficial to improving the rate performance of the battery.

[0100] Table 1

[0101] Porous carbon materials <![CDATA[Specific surface area m 2 / g]]> <![CDATA[Total pore volume cm 3 / g]]> Does XRD show graphite characteristic peaks? Example 1 2497 1.15 yes Example 2 2210 1.01 yes Example 3 2380 1.12 yes Example 4 2310 1.08 yes Example 5 2290 1.07 yes Example 6 2270 1.05 yes Example 7 2260 1.03 yes Comparative Example 1 2150 1.02 no Comparative Example 2 2140 0.93 no Comparative Example 3 2190 0.90 no Comparative Example 4 1500 0.78 yes

[0102] As shown in Table 1, the porous carbon materials prepared in Examples 1-7 of this application all exhibit graphite characteristic peaks after XRD testing. The specific surface area of ​​the porous carbon materials prepared in Examples 1-7 of this application can all reach 2200 m². 2 / g or more, with a pore volume up to 1.0 cm³. 3 A concentration of / g or higher is beneficial for silicon deposition, thereby improving the capacity and cycle performance of silicon-carbon anode active materials.

[0103] like Figure 1 As shown, the porous carbon material of Example 1 exhibits a characteristic peak at 2θ = 26.3° as determined by XRD, proving that the porous carbon material of this application achieves a soft-hard carbon composite. In contrast, Comparative Example 1, which was not heat-treated, showed no graphite characteristic peak in its XRD test, indicating that the porous carbon material prepared in Comparative Example 1 does not contain soft carbon and is a hard carbon material.

[0104] Table 2

[0105]

[0106] As shown in Table 2, the ultra-high capacity silicon-carbon anode active materials prepared by depositing silicon using porous carbon materials with soft and hard carbon composites in Examples 1-7 of this application exhibit high capacity, high initial efficiency, good cycle stability, and conductivity. The anode active materials prepared in Examples 1-7 can achieve a discharge capacity of over 2350 mAh / g, a reversible capacity of over 2000 mAh / g at 0.8V, an initial efficiency of over 84%, and the powder resistivity can be maintained below 20 Ω*cm, demonstrating excellent electrochemical performance.

[0107] In Comparative Example 1, compared with Example 1, no heat treatment was performed, which prevented the graphitization of the soft carbon portion in the porous carbon material, resulting in poor electrical conductivity and high powder resistivity.

[0108] In Comparative Example 2, compared with Example 1, no soft carbon resin precursor was introduced into the raw materials for preparing porous carbon materials, and the resulting porous carbon materials were hard carbon, resulting in poor conductivity of porous carbon materials. The resistivity of the silicon-carbon anode active material powder was as high as 31 Ω*cm.

[0109] In Comparative Example 3, compared with Example 1, the heat treatment temperature was lower, which was not conducive to the graphitization of the soft carbon precursor, and soft carbon could not be produced, affecting the conductivity and causing the powder resistivity to increase to 23.5 Ω*cm.

[0110] In Comparative Example 4, compared with Example 1, the heat treatment temperature was higher, which caused a large number of closed pores to be generated in the porous carbon material, and even pore collapse occurred, making it impossible to effectively load a large amount of silicon, resulting in a significant decrease in capacity.

[0111] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for producing a porous carbon material, characterized by, Includes the following steps: a. Mix hard carbon resin precursor and soft carbon resin precursor to obtain resin precursor material; b. Mix the resin precursor material obtained in step a with an alkaline activator, perform activation treatment, and then wash and dry to obtain a porous carbon material precursor. c. The porous carbon material precursor obtained in step b is placed in an inert atmosphere and heat-treated at 1300-2000℃ to obtain porous carbon material.

2. The method for preparing porous carbon materials according to claim 1, characterized in that, In step a, the hard carbon resin precursor includes phenolic resin. Preferably, the raw materials for preparing the hard carbon resin precursor include phenol and formaldehyde. More preferably, the molar ratio of phenol to formaldehyde is 2-4:

1. And / or, the soft carbon resin precursor includes at least one of polyvinylpyrrolidone, polyethylene glycol, or polyethylene; And / or, the mass ratio of the hard carbon resin precursor to the soft carbon resin precursor is 1-2:

1.

3. The method for preparing porous carbon materials according to claim 1, characterized in that, In step b, the alkaline activator includes potassium hydroxide; And / or, in step b, the mass ratio of carbon to alkaline activator in the resin precursor material is 1:(2-8); And / or, in step b, the activation treatment is carried out in an inert atmosphere, the activation temperature is 700-900℃, and the activation time is 3-8h; And / or, in step b, the washing process involves sequentially washing with hydrochloric acid and deionized water until neutral; And / or, in step c, the inert atmosphere uses at least one of nitrogen or argon; And / or, in step c, the heat treatment time is 2-4 hours.

4. A porous carbon material, characterized in that, It is prepared by any one of claims 1-3.

5. A silicon-carbon anode active material, characterized in that, The silicon-carbon anode active material includes a porous carbon material and silicon distributed within the porous carbon material, wherein the porous carbon material is a porous carbon material prepared by any one of claims 1-3 or a porous carbon material as described in claim 4.

6. A method for preparing the silicon-carbon anode active material according to claim 5, characterized in that, Includes the following steps: (1). Using porous carbon material as raw material, silicon source is introduced under inert protective gas to perform silicon deposition and obtain silicon-carbon core; (2). The material obtained after silicon deposition in step a is subjected to carbon coating treatment to obtain silicon-carbon anode active material.

7. The method for preparing the silicon-carbon anode active material according to claim 6, characterized in that, In step (1), the silicon source includes at least one of silane or silane; And / or, the mass ratio of the silicon source to the porous carbon material is (1.5-2):1; And / or, the inert protective gas includes at least one of nitrogen or argon; And / or, the silicon source is introduced at a rate of 1-5 L / min; And / or, in the silicon deposition, the silicon deposition temperature is 480℃-580℃ and the time is 5-10h.

8. The method for preparing the silicon-carbon anode active material according to claim 6, characterized in that, In step (2), acetylene is used for carbon coating treatment. Preferably, the acetylene introduction rate is 1-5 L / min, the carbon coating treatment temperature is 550-600℃, and the carbon coating treatment time is 1-5 h.

9. A secondary battery, characterized in that, Includes the silicon-carbon anode active material as described in claim 5 or the silicon-carbon anode active material prepared by the method described in any one of claims 6-8.

10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.

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