Screening method for high-density hard carbon, high-density hard carbon and preparation method and application thereof

Abstract

The application belongs to the technical field of negative electrode materials, and particularly relates to a screening method of high-pressing-density hard carbon, the high-pressing-density hard carbon and a preparation method and application thereof. The application provides a screening method of high-pressing-density hard carbon, which comprises the following steps: testing the particle size of the to-be-tested hard carbon by using a laser particle size analyzer, obtaining a particle size distribution curve and a maximum particle size D max and a minimum particle size D min ; substituting any particle size in the particle size distribution curve into formula I to calculate an n value, X(D) = (D n -D min n ) / (D max n -D min n ) formula I; if the n value satisfies 1 / 3 < n < 1 / 2, the to-be-tested hard carbon is high-pressing-density hard carbon; the X(D) is a volume fraction of the particle size, and the value range is 1-100%; the D is the particle size of any particle size in the particle size distribution curve. The screening method provided by the application can obtain high-pressing-density hard carbon material.

Description

Technical Field

[0001] This invention belongs to the field of negative electrode material technology, specifically relating to a screening method for high-pressure dense hard carbon, high-pressure dense hard carbon and its preparation method and application. Background Technology

[0002] Currently, the main types of rechargeable batteries on the market include lithium-ion batteries, sodium-ion batteries, supercapacitors, nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid (or lead-acid) batteries, and rechargeable alkaline batteries. The negative electrode material is the carrier of ions and electrons during the charging process of a rechargeable battery, playing a role in energy storage and release. Hard carbon has great application potential as a negative electrode material for rechargeable batteries. However, because the compaction density of hard carbon is significantly lower than that of graphite, constructing hard carbon materials with high compaction density is of great significance for improving the energy density of rechargeable batteries. Summary of the Invention

[0003] The purpose of this invention is to provide a screening method for high-pressure dense hard carbon, high-pressure dense hard carbon, its preparation method and application. The screening method provided by this invention can obtain high-pressure dense hard carbon.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for screening high-density hard carbon, comprising the following steps:

[0006] The particle size of the hard carbon sample was measured using a laser particle size analyzer, and the particle size distribution curve and the maximum particle size D were obtained. max and minimum particle size D min ;

[0007] Substitute any particle size from the particle size distribution curve into Equation I to calculate the value of n.

[0008] X(D)=(D n -D min n ) / (D max n -D min n Formula I;

[0009] If the value of n satisfies 1 / 3 < n < 1 / 2, then the hard carbon to be tested is high-pressure dense hard carbon.

[0010] X(D) is the volume fraction of particle size, and its value ranges from 1 to 100%.

[0011] D represents the particle size of any particle size in the particle size distribution curve.

[0012] Preferably, the value of X(D) is 10%, 20%, 35%, 50%, 90%, 99%, or 100%.

[0013] This invention also provides a method for preparing high-density hard carbon, comprising the following steps:

[0014] The hard carbon raw material is subjected to low-temperature treatment to obtain pretreated hard carbon raw material;

[0015] The pretreated hard carbon raw material is subjected to particle size adjustment, and the screened hard carbon raw material is obtained according to the screening method described in the above technical solution.

[0016] The screened hard carbon raw materials were sequentially purified and subjected to high-temperature treatment to obtain the high-pressure dense hard carbon.

[0017] Preferably, the hard carbon raw material includes one or more of biomass, resin, coal-based raw materials, bitumen, and biological extracts.

[0018] Preferably, the temperature of the low-temperature treatment is 500–900°C, and the holding time is 1–8 hours.

[0019] Preferably, the equipment used for particle size adjustment includes one or more of the following: jaw crusher, roller crusher, double roller crusher, hammer crusher, impact crusher, vertical crusher, universal pulverizer, cryogenic pulverizer, hammer mill, ultra-micro impact mill, flat air jet mill, fluidized bed jet mill, ball mill, circulating tube air jet mill, jet mill, VC mixer, and target air jet mill.

[0020] The purification process includes one or more of the following: acid washing, alkali washing, and water washing.

[0021] Preferably, the high-temperature treatment is performed at a temperature of 900–1500°C for 1–8 hours.

[0022] The present invention also provides high-density hard carbon prepared by the preparation method described in the above technical solution.

[0023] Preferably, the high-pressure compaction density hard carbon has a powder compaction density of 0.80–1.05 g / cm³ at a pressure of 1 ton. 3 The compacted density of the powder is 0.85–1.10 g / cm³ when the pressure is 2 tons. 3 The compacted density of the powder is 0.90–1.25 g / cm³ when the pressure is 3 tons. 3 When the high-density hard carbon is pressed into a negative electrode sheet using a roller press, the compaction density of the negative electrode sheet is 0.90–1.25 g / cm³. 3 .

[0024] The present invention also provides the application of the high-density hard carbon described in the above technical solution as a negative electrode material in batteries or capacitors.

[0025] This invention provides a method for screening high-density hard carbon, comprising the following steps: using a laser particle size analyzer to test the particle size of the hard carbon to be tested, obtaining the particle size distribution curve and the maximum particle size D. max and minimum particle size D min Substitute any particle size from the particle size distribution curve into Equation I to calculate the value of n: X(D) = (D n -D min n ) / (D max n -D min n Formula I; if the value of n satisfies 1 / 3 < n < 1 / 2, then the hard carbon to be tested is high-pressure dense hard carbon; X(D) is the volume fraction of particle size, ranging from 1 to 100%; D is the particle size of any particle size in the particle size distribution curve. The screening method provided by this invention can obtain high-pressure dense hard carbon materials. Attached Figure Description

[0026] Figure 1 Here is a SEM image of the hard carbon obtained in Example 1;

[0027] Figure 2 The image shows the particle size distribution curve of the hard carbon obtained in Example 1. Detailed Implementation

[0028] This invention provides a method for screening high-density hard carbon, comprising the following steps:

[0029] The particle size of the hard carbon sample was measured using a laser particle size analyzer, and the particle size distribution curve and the maximum particle size D were obtained. max and minimum particle size D min ;

[0030] Substitute any particle size from the particle size distribution curve into Equation I to calculate the value of n.

[0031] X(D)=(D n -D min n ) / (D max n -D min n Formula I;

[0032] If the value of n satisfies 1 / 3 < n < 1 / 2, then the hard carbon to be tested is high-pressure dense hard carbon.

[0033] X(D) is the volume fraction of particle size, and its value ranges from 1 to 100%.

[0034] D represents the particle size of any particle size in the particle size distribution curve.

[0035] The present invention does not impose any special limitations on the process of using a laser particle size analyzer to test the particle size of the hard carbon to be tested; any process known to those skilled in the art can be used.

[0036] In this invention, the value of X(D) ranges from 1 to 100%, preferably 10%, 20%, 35%, 50%, 90%, 99%, or 100%. In this invention, when X(D) is 10%, D is the particle size of D10; when X(D) is 20%, D is the particle size of D20, and so on.

[0037] This invention also provides a method for preparing high-density hard carbon, comprising the following steps:

[0038] The hard carbon raw material is subjected to low-temperature treatment to obtain pretreated hard carbon raw material;

[0039] The pretreated hard carbon raw material is subjected to particle size adjustment, and the screened hard carbon raw material is obtained according to the screening method described in the above technical solution.

[0040] The screened hard carbon raw materials were sequentially purified and subjected to high-temperature treatment to obtain the high-pressure dense hard carbon.

[0041] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0042] This invention involves subjecting hard carbon raw materials to low-temperature treatment to obtain pretreated hard carbon raw materials.

[0043] In this invention, the hard charcoal raw material preferably includes one or more of biomass, resin, coal-based raw materials, asphalt, and bio-extractants. In this invention, the biomass preferably includes one or more of apricot shells, walnut shells, jujube shells, plum shells, rice husks, peanut shells, camellia shells, pistachio shells, coconut shells, wood, bamboo, hazelnuts, and straw, more preferably apricot shells, bamboo, or straw. In this invention, when the biomass includes two or more of the above-mentioned specific substances, the proportions of the specific substances are not particularly limited, and any proportion can be used. In this invention, the raw material resin preferably includes one or more of phenolic resin, epoxy resin, furfural resin, and acrylic resin, more preferably phenolic resin or acrylic resin. In this invention, when the resin material includes two or more of the above-mentioned specific substances, the proportions of the specific substances are not particularly limited, and any proportion can be used. In this invention, the asphalt preferably includes one or more of petroleum asphalt, coal tar pitch, and natural asphalt, more preferably petroleum asphalt. In this invention, when the asphalt includes two or more of the above-mentioned specific substances, the proportions of the specific substances are not particularly limited, and any proportion can be used. In this invention, the bio-extract preferably includes one or more of starch, sucrose, glucose, cellulose, maltose, and natural rubber, more preferably starch or cellulose. In this invention, when the bio-extract includes two or more of the above-mentioned specific substances, the proportions of the specific substances are not particularly limited, and any proportion can be used. In this invention, the coal-based raw material preferably includes one or more of bituminous coal, anthracite, or lignite, more preferably anthracite.

[0044] In this invention, the preferred temperature for the low-temperature treatment is 500–900°C, and the preferred holding time is 1–8 hours. The main purpose of the low-temperature treatment is to remove most of the volatile matter from the raw materials, obtaining a basically stable carbon framework structure. If the low-temperature treatment temperature is too low, insufficient volatile matter removal will lead to an unstable carbon framework structure; if the temperature is too high, it will increase energy consumption and process costs. Therefore, the low-temperature treatment temperature should preferably be within the preferred range. After the low-temperature treatment, this invention also preferably includes cooling the obtained material to room temperature.

[0045] After obtaining the pretreated hard carbon raw material, the present invention adjusts the particle size of the pretreated hard carbon raw material and obtains screened hard carbon raw material according to the screening method described in the above technical solution.

[0046] In this invention, the equipment used for particle size adjustment preferably includes one or more of the following: jaw crusher, roller crusher, double roller crusher, hammer crusher, impact crusher, vertical crusher, universal pulverizer, cryogenic pulverizer, hammer mill, ultrafine impact mill, flat air jet mill, fluidized bed jet mill, ball mill, circulating tube air jet mill, jet mill, VC mixer, and target air jet mill. This invention does not impose any special limitations on the specific process of particle size adjustment; any process well-known to those skilled in the art can be used. The main purpose of particle size adjustment in this invention is to ensure that the hard carbon has a suitable particle size to meet the screening method described in the above technical solution. Through reasonable particle arrangement, fewer voids are created between particles, resulting in a higher compaction density.

[0047] After obtaining the screened hard carbon raw material, the present invention purifies and processes the screened hard carbon raw material at high temperature in sequence to obtain the high-pressure dense hard carbon.

[0048] In this invention, the purification preferably includes one or more of acid washing, alkali washing, and water washing. In this invention, the acid reagent used for acid washing preferably includes one or more of hydrofluoric acid, sulfurous acid, phosphoric acid, nitrous acid, sulfuric acid, hydrochloric acid, and nitric acid, more preferably hydrochloric acid and hydrofluoric acid; the concentration of the acid reagent is preferably 0.1–5 mol / L, more preferably 0.5–1.5 mol / L. In this invention, the alkali reagent used for alkali washing preferably includes one or more of sodium hydroxide solution, ammonia solution, calcium hydroxide solution, and potassium hydroxide solution, more preferably sodium hydroxide solution; the concentration of the alkali reagent is preferably 0.5–5 mol / L, more preferably 1–2.5 mol / L. In this invention, the water washing preferably uses deionized water. In this invention, the purification removes potassium, sodium, calcium, magnesium, and magnetic substances, reduces side reactions of the binder, thereby improving the adhesion between hard carbon particles and between hard carbon particles and the current collector, thus increasing the compaction density of the hard carbon; when used as a negative electrode material, it further improves the stability of the material.

[0049] In this invention, the preferred temperature for the high-temperature treatment is 900–1500°C, and the preferred holding time is 1–8 hours. The main purpose of the high-temperature treatment is to improve the compactness of the internal carbon structure of the hard carbon, thereby increasing its compaction density. The high-temperature treatment also reduces defects in the hard carbon material, thus improving the initial efficiency and cycle stability of the secondary battery. After the high-temperature treatment, this invention preferably further includes cooling the obtained material to room temperature.

[0050] In this invention, both the low-temperature treatment and the high-temperature treatment are preferably carried out in a protective atmosphere; the protective atmosphere is preferably one of nitrogen, helium, neon and argon.

[0051] The present invention also provides high-density hard carbon prepared by the preparation method described in the above technical solution.

[0052] In this invention, the compaction density of the high-pressure compacted hard carbon powder is preferably 0.80–1.05 g / cm³ at a pressure of 1 ton. 3 Further preferably, it is 0.88–1.05 g / cm³. 3 When the pressure is 2 tons, the preferred compaction density of the powder is 0.85–1.10 g / cm³. 3 Further preferably, it is 0.92–1.10 g / cm³. 3 When the pressure is 3 tons, the preferred compaction density of the powder is 0.90–1.25 g / cm³. 3 Further preferably, it is 0.97–1.25 g / cm³. 3 In this invention, the compacted density of the powder is preferably tested using a powder compactor.

[0053] In this invention, when the high-compact-density hard carbon is pressed into a negative electrode sheet using a roller press, the compaction density of the negative electrode sheet is preferably 0.90–1.25 g / cm³. 3 More preferably, it is 0.95–1.25 g / cm³. 3 In this invention, the higher the compaction density of the negative electrode sheet, the higher the energy density of the battery after it is made into a battery.

[0054] In this invention, the specific surface area of ​​the high-density hard carbon is preferably 1 to 25 m². 2 / g, more preferably 2-10m 2 / g. In this invention, if the specific surface area of ​​the hard carbon material is too high, the initial efficiency of the resulting secondary battery will be low. Therefore, the specific surface area should be within a preferred range, which is mainly adjusted by different high-temperature treatment temperatures in the high-temperature treatment process.

[0055] This invention also provides the application of the high-density hard carbon described above as a negative electrode material in batteries or capacitors. In this invention, the battery preferably includes a lithium-ion battery or a sodium-ion battery.

[0056] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, provides a method for screening high-pressure dense hard carbon, the high-pressure dense hard carbon itself, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] Take 10 kg of corn stalks and keep them at 500℃ for 3 hours in a nitrogen atmosphere. After cooling to room temperature, sintered material is obtained.

[0059] The sintered material was subjected to particle size adjustment using a fluidized bed jet mill. The particle size of the resulting material was measured using a laser particle size analyzer. Based on Formula I, the particle size of the material was adjusted to: D min It is 0.6μm, D max The particle size was 27.8 μm, D10 was 1.2 μm, and D50 was 5.6 μm. The obtained material was successively acid-washed with 1 mol / L hydrochloric acid and 1 mol / L hydrofluoric acid, and then washed with deionized water until the filtrate was neutral to obtain the hard carbon precursor.

[0060] In a nitrogen atmosphere, the hard carbon precursor was subjected to high-temperature treatment at 1250°C for 2.5 hours, and then cooled to room temperature to obtain the high-pressure dense hard carbon.

[0061] Example 2

[0062] Take 10 kg of corn starch and keep it at 650℃ for 3.5 h in a nitrogen atmosphere. After cooling to room temperature, sintered material is obtained.

[0063] The sintered material was subjected to particle size adjustment using a ball mill. The particle size of the resulting material was then measured using a laser particle size analyzer. Based on Formula I, the particle size of the material was adjusted to: D min It is 0.8μm, D max The particle size was 36.4 μm, D25 was 4.1 μm, and D50 was 7.2 μm. The obtained materials were washed sequentially with deionized water until the filtrate was neutral to obtain the hard carbon precursor.

[0064] In a nitrogen atmosphere, the hard carbon precursor was subjected to high-temperature treatment at 1150°C for 4 hours, and then cooled to room temperature to obtain the high-pressure dense hard carbon.

[0065] Example 3

[0066] Take 10 kg of phenolic resin and keep it at 700℃ for 3 hours in a nitrogen atmosphere. After cooling to room temperature, the sintered material is obtained.

[0067] The sintered material was subjected to particle size adjustment using a circulating tubular air jet mill. The particle size of the resulting material was measured using a laser particle size analyzer. Based on Formula I, the particle size of the material was adjusted to: D min It is 1.1 μm, D max The particle size was 43.7 μm, D35 was 7.2 μm, and D50 was 9.8 μm. The obtained material was acid-washed sequentially with hydrochloric acid at a concentration of 2.5 mol / L and hydrofluoric acid at a concentration of 1.5 mol / L, and then washed with deionized water until the filtrate was neutral to obtain the hard carbon precursor.

[0068] In a nitrogen atmosphere, the hard carbon precursor was subjected to high-temperature treatment at 1350°C for 4 hours, and then cooled to room temperature to obtain the high-pressure dense hard carbon.

[0069] Example 4

[0070] Take 10 kg of anthracite and hold it at 700℃ for 2 hours in a nitrogen atmosphere. After cooling to room temperature, the sintered material is obtained.

[0071] The sintered material was subjected to particle size adjustment using a VC mixer. The particle size of the resulting material was then measured using a laser particle size analyzer. Based on Formula I, the particle size of the material was adjusted to: D min It is 0.7μm, D max The particle size was 51.2 μm, the D90 was 37.2 μm, and the D50 was 8.5 μm. The obtained materials were washed with deionized water until the filtrate was neutral to obtain the hard carbon precursor.

[0072] In a nitrogen atmosphere, the hard carbon precursor was subjected to high-temperature treatment at 1100°C for 4 hours, and then cooled to room temperature to obtain the high-pressure dense hard carbon.

[0073] Comparative Example 1

[0074] Hard carbon was prepared according to the method in Example 1, except that the particle size was adjusted to the particle size D of the material. min It is 0.2μm, D max The value is 17.8 μm, D10 is 1.1 μm, and D50 is 3.9 μm.

[0075] Comparative Example 2

[0076] Hard carbon was prepared according to the method in Example 1, except that the acid washing and water washing steps were omitted.

[0077] Comparative Example 3

[0078] Hard carbon was prepared according to the method of Example 1, except that the high-temperature treatment temperature was adjusted to 850°C.

[0079] Comparative Example 4

[0080] Take 10 kg of corn stalks and keep them at 200℃ for 3 hours in a nitrogen atmosphere. After cooling to room temperature, sintered material is obtained.

[0081] The sintered material was subjected to particle size adjustment using a fluidized bed jet mill, and the resulting material was tested for particle size using a laser particle size analyzer. The particle size of the material was: D min It is 0.9μm, D maxThe particle size is 34.2 μm, D10 is 3.8 μm, and D50 is 7.7 μm. Due to the excessively low temperature of the low-temperature treatment, the pre-carbonization of the sintered material is incomplete, the structure is not compact, and the particle size cannot meet the requirements of Formula I when adjusting the particle size.

[0082] The obtained material was successively acid-washed with 1 mol / L hydrochloric acid and 1 mol / L hydrofluoric acid, and then washed with deionized water until the filtrate was neutral to obtain the hard carbon precursor.

[0083] In a nitrogen atmosphere, the hard carbon precursor was subjected to high-temperature treatment at 1250℃ for 2.5h, and then cooled to room temperature to obtain the hard carbon material.

[0084] Performance testing

[0085] Test Example 1

[0086] The hard carbon prepared in Example 1 was analyzed by SEM using a JSM-7160 scanning electron microscope from Nippon Electronics Corporation. The obtained SEM images are shown below. Figure 1 As shown. By Figure 1 It can be seen that the hard carbon particles prepared in Example 1 have fewer gaps between them.

[0087] Test Example 2

[0088] The particle size distribution of the material was tested using a Dandong Better Laser Particle Size Analyzer BT-9300ST. The results are shown in Table 1. The particle size distribution curve for Example 1 is shown below. Figure 2 As shown.

[0089] Test Example 3

[0090] The specific surface area of ​​the material was tested using the American CANTA NOVA4000e, and the results are shown in Table 1.

[0091] The hard carbon obtained in Examples 1-4 and Comparative Examples 1-4 was mixed with conductive carbon black and binder in pure water at a mass ratio of 96:1:3 and stirred evenly to obtain a slurry with a solid content of 48%. The slurry was coated on a copper foil current collector, baked in vacuum at 105°C for 6 hours, pressed into shape, and its electrode compaction density was tested. The results are shown in Table 1.

[0092] Table 1. Test data of hard carbon materials in Examples 1-4 and Comparative Examples 1-4.

[0093]

[0094]

[0095] Based on the data in Table 1, it can be concluded that different types of raw materials, after low-temperature treatment, particle size adjustment, purification and high-temperature treatment, all produce hard carbon with high powder compaction density and electrode compaction density. The compaction density also varies with different raw materials and process conditions, with coal-based raw materials having higher compaction density.

[0096] In Comparative Example 1, because the particle size distribution was outside the screening conditions during particle size adjustment, both powder compaction and electrode compaction were significantly lower than in Example 1. In Comparative Example 2, although the powder compaction was higher due to the lack of purification treatment, the electrode compaction was significantly lower than in Example 1. This was because the lack of purification treatment resulted in a higher impurity content in the hard carbon material, which reacted with the binder, leading to poor adhesion and reduced compaction density. In Comparative Example 3, due to the excessively low high-temperature treatment temperature, the hard carbon material had too many internal defects, resulting in a significantly larger specific surface area. These excessive defects led to a loose internal structure, resulting in relatively low powder compaction and electrode compaction. In Comparative Example 4, due to the excessively low low-temperature treatment temperature, the sintered material underwent incomplete pre-carbonization, resulting in a loose structure. The particle size adjustment could not meet the requirements of Formula I, thus leading to relatively low powder compaction and electrode compaction.

[0097] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A screening method of high-compact-density hard carbon, characterized by, The method comprises the following steps: The particle size of the hard carbon to be tested is tested by using a laser particle size analyzer to obtain a particle size distribution curve and a maximum particle size D max and a minimum particle size D min ; The n value is calculated by substituting any particle size in the particle size distribution curve into Formula I, X(D) = (D n - D min n ) / (D max n - D min n ) Equation I; If the n value satisfies 1 / 3 The X(D) is the volume fraction of the particle size, and the value range is 1-100%; The D is the particle size of any particle size in the particle size distribution curve.

2. The screening method according to claim 1, characterized in that, The value of the X(D) is 10%, 20%, 35%, 50%, 90%, 99% or 100%.

3. A method for producing a high-density hard carbon, characterized by, The method comprises the following steps: The hard carbon raw material is subjected to low-temperature treatment to obtain pretreated hard carbon raw material; The pretreated hard carbon raw material is subjected to particle size adjustment, and the screened hard carbon raw material is obtained according to the screening method of claim 1 or 2; The screened hard carbon raw material is sequentially subjected to purification and high-temperature treatment to obtain the high-compactness hard carbon.

4. The production method according to claim 3, characterized by, The hard carbon raw material comprises one or more of biomass, resin, coal-based raw material, pitch and biological extract.

5. The preparation method according to claim 3, characterized in that, The temperature of the low-temperature treatment is 500-900 DEG C, and the holding time is 1-8 h.

6. The preparation method according to claim 3, characterized in that, The equipment for the particle size adjustment comprises one or more of a jaw crusher, a roller crusher, a double-roller crusher, a hammer crusher, an impact crusher, a vertical crusher, a universal pulverizer, a deep-cooling pulverizer, a machine hammer piece type pulverizer, an ultramicro impact mill, a flat airflow mill, a fluidized bed counter-jet airflow mill, a ball mill, a circulating pipe airflow mill, a counter-jet airflow mill, a VC mixer and a target airflow mill. The purification comprises one or more of acid washing, alkali washing and water washing.

7. The preparation method according to claim 3, characterized in that, The temperature of the high-temperature treatment is 900-1500 DEG C, and the holding time is 1-8 h.

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