Method for controlling interlayer spacing of hard carbon material structure by electrolytic intercalation

Abstract

The application discloses a method for controlling the interlayer spacing of a hard carbon material structure by using an electrolytic embedding technique. In a nitrogen atmosphere, impure coal is sintered in a first stage to obtain primary sintered coal; in an acid solution, the primary sintered coal is used as an anode and an inert electrode is used as a cathode to electrolyze the primary sintered coal and obtain electrolytic coal; the electrolytic coal is washed and dried to obtain dry coal; in a nitrogen atmosphere, the dry coal is sintered in a second stage with a stepwise temperature rise to obtain coal with a controlled expansion degree; nitrogen is introduced into a reaction kettle, the coal with a controlled expansion degree is added, a phenolic compound and an aldehyde compound are mixed, heating treatment is performed, and a catalyst is added to obtain a composite sample of the coal with a controlled expansion degree and a thermoplastic phenolic resin; in a nitrogen atmosphere, the composite sample of the coal with a controlled expansion degree and the thermoplastic phenolic resin is sintered in a third stage to obtain a coated hard carbon material with a controlled expansion degree. The sample prepared by the method has small surface pores, high coulomb efficiency for charging and discharging, and good cycle stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of battery electrode material preparation, and particularly relates to a method for controlling the interlayer spacing of a hard carbon material structure by electrolytic intercalation technology, which can be used in lithium batteries, lithium ion batteries, sodium batteries, sodium ion batteries and supercapacitors. BACKGROUND

[0002] Sodium ion batteries have the advantages of abundant resource, long cycle life and good low-temperature performance. Hard carbon is commonly used as the negative electrode material of sodium ion batteries. The charge-discharge capacity, first cycle coulombic efficiency and charge-discharge performance of the hard carbon negative electrode material play a key role in the electrochemical performance and safe use of sodium ion batteries.

[0003] Hard carbon material is composed of short-range ordered microzones of curved graphite-like sheets stacked. When the hard carbon negative electrode material is charged and discharged, due to the large ionic radius of sodium ions, the kinetics of sodium ions intercalating / deintercalating in the hard carbon is poor, which makes the rate performance of the hard carbon negative electrode material poor. Therefore, the morphology of the hard carbon material has been designed to increase the diffusion channel of sodium ions, thereby improving the rate discharge performance of the hard carbon material. The hard carbon negative electrode materials that have been studied include zero-dimensional carbon quantum dots, one-dimensional carbon fibers, two-dimensional carbon nanosheets, three-dimensional carbon spheres, carbon frameworks, and hollow structures, porous structures, hierarchical structures, hollow carbon nanospheres, nanowires, N-doped porous carbon nanosheets, etc. Nanosized hard carbon materials can effectively improve their rate discharge performance. However, nanosized hard carbon materials have a significantly increased specific surface area, which will form a large amount of SEI film during the first cycle of charging and discharging, significantly reducing the coulombic efficiency of the first cycle and subsequent charging and discharging cycles, and increasing the probability of side reactions, making the prepared samples exhibit poor cycle performance. Such hard carbon materials are prone to swelling and other problems during the charging and discharging process. At present, there are different views on the intercalation mechanism of sodium ions in hard carbon materials, indicating that the key factors affecting the charge-discharge performance of hard carbon materials have not yet reached a consensus.

[0004] The morphology and carbonization process of hard carbon precursor determine the structure and performance of hard carbon. The raw materials for preparing hard carbon precursor can be selected from biomass precursors, non-biomass precursors and compound precursors. The biomass precursor approach has the advantages of simple preparation process and low cost. However, the biomass precursor is greatly affected by the source of biomass. For example, the use of coconut shell as a carbon source for hard carbon negative electrode material is greatly limited by its annual production capacity. Because the biomass contains unevenly distributed doping ions. The place of origin and batch of biomass also have a significant impact on the performance of the prepared hard carbon material. Therefore, the hard carbon prepared by this approach has batch inconsistency problem. The compound precursor is an organic polymer prepared from monomer compounds. When this organic polymer is used as a carbon source for hard carbon, the prepared hard carbon has a high discharge capacity. This approach for preparing hard carbon has the advantages of stable raw material source, determined composition of compound precursor, and less impurities in the precursor. However, this method for preparing the precursor has the problems of complex process and high cost.

[0005] The preparation of hard carbon materials generally consists of two main steps: precursor preparation and high-temperature sintering. The preparation methods of hard carbon precursors include spray drying, hydrothermal method, electrospinning and sol-gel method, etc. Spray drying method is easy to be applied in industry. However, this method has some problems: the temperature of spray drying is low, and the prepared material needs further sintering treatment. The samples prepared by spray drying method also have some problems such as unstable structure, poor discharge performance, etc. In view of the low discharge capacity of hard carbon materials prepared by phenolic resin precursor, the predecessors (Lü WJ, Modified phenolic resin-based hard carbon and its sodium storage performance, Tianjin University of Technology, Master's degree thesis, 2020.12.) used epoxy small molecule compounds to combine with spray drying method to prepare ordinary phenolic resin. This method can change the oxygen-containing functional groups, the interlayer spacing of graphite microcrystalline layer and the degree of graphitization in hard carbon materials. The sample treated by sintering at 900℃ shows the best electrochemical performance, with an initial discharge capacity of 287mAh / g and a coulombic efficiency of 83.32% in the first cycle. Wang et al. prepared phenolic resin graphene composite three-dimensional network hard carbon materials by spray drying method. The addition of high-conductivity graphene in this material can significantly improve the large-current discharge performance of hard carbon materials. Hu et al. prepared resorcinol-formaldehyde-based phenolic resin by two-step hydrothermal method, and then sintered at 1400℃ to prepare hard carbon with an initial discharge capacity of 400mAh / g. A mixture of glyoxalic acid, resorcinol, oxalic acid, water and ethanol was hydrothermally treated at 200℃ to obtain modified phenolic resin. The phenolic resin was sintered at 1300℃ in a nitrogen atmosphere to prepare hard carbon materials with an initial discharge capacity of 325mAh / g and a coulombic efficiency of 88.59% in the first cycle. Tian et al. mixed resorcinol, formaldehyde and polyvinyl alcohol into a spinning solution to prepare phenolic-based carbon nanofibers by electrospinning method. George et al. used sol-gel method to prepare resorcinol-formaldehyde-based phenolic resin, and then carbonized at high temperature to prepare self-supporting hard carbon materials.

[0006] The dehydration and condensation reaction of phenolic resin precursor will occur during heating treatment, forming a highly cross-linked refractory phenolic polymer. The pyrolysis process of this refractory phenolic polymer will form hard carbon with high carbon yield. Although years of research, the hard carbon prepared by phenolic resin still has some problems such as low discharge capacity, low cycle stability, low charge-discharge coulombic efficiency, etc. Previous studies have shown that the structure, composition and preparation method of phenolic resin have a great influence on the electrochemical performance of the prepared hard carbon. Improving the structure and composition of phenolic resin precursor may significantly improve its performance. Chemical method can improve the performance of phenolic resin precursor, and has good improvement effect.

[0007] China has abundant coal resources, and it has been reported that the performance of coal can be improved by preliminary pyrolysis and coating pyrolyzed coal with phenolic resin. However, pyrolyzed coal contains a large number of internal pores and cavities, and previous researchers have failed to make phenolic resin penetrate into the inner layer and internal pores of coal particles. The hard carbon prepared by this method cannot coat the pores and cavities in the pyrolyzed coal particles. With the charging and discharging cycles, the sodium ions embedded and extracted in the coal crystallite will cause the internal nanopores and cavities of the coal-based hard carbon particles to be exposed to the electrolyte of the battery system, and side reactions will occur between the electrolyte and the electrolyte, reducing the coulombic efficiency and the stability of the charging and discharging cycles. The hard carbon material prepared from coal also has problems such as low coulombic efficiency, low discharge capacity, low cycle life, and slow reaction kinetics, which hinder its practical application. Although various modification methods have been reported, the improvement effect is still not obvious. SUMMARY

[0008] In order to improve the performance of hard carbon material, the method for controlling the structure layer spacing of hard carbon material by electrolytic embedding technology is adopted to prepare the hard carbon material.

[0009] In order to achieve the above object, the technical scheme adopted by the present application is as follows:

[0010] The method for controlling the structure layer spacing of hard carbon material by electrolytic embedding technology comprises the following steps:

[0011] 1) Under a nitrogen atmosphere, the impure coal is subjected to first-stage sintering to obtain preliminarily sintered coal;

[0012] 2) In an acidic solution, the preliminarily sintered coal is used as an anode and an inert electrode is used as a cathode, and electrolysis is carried out at a current density of 2-50 mA / cm 2 for 0.5-6 h to obtain electrolyzed coal;

[0013] 3) The electrolyzed coal is washed and dried to obtain dried coal;

[0014] 4) Under a nitrogen atmosphere, the dried coal is subjected to second-stage sintering with a stepwise temperature rise to obtain coal with controlled expansion degree;

[0015] 5) In a reaction kettle, nitrogen is introduced, and coal with controlled expansion degree is added, followed by mixing with a weighed amount of phenolic compound and aldehyde compound; continuous stirring and mixing are carried out, and heating is carried out to 80-98℃; a catalyst with a weight of 0.1wt.%-5wt.% of the phenolic compound is added, and heat preservation is carried out for 3-10 h to obtain a composite sample of coal with controlled expansion degree-thermoplastic phenolic resin;

[0016] 6) Under a nitrogen atmosphere, the composite sample of coal with controlled expansion degree-thermoplastic phenolic resin is subjected to third-stage sintering to obtain hard carbon material with controlled expansion degree coating.

[0017] The molar ratio of the phenolic compound to the aldehyde compound is 1:0.2-0.95; the weight ratio of the impurity-removed coal to the phenolic compound is 1:0.3-2.2.

[0018] The first-stage sintering is first-stage programmed temperature sintering; the first-stage programmed temperature sintering is heating the impurity-removed coal to 750-1100℃ at a heating rate of 15℃ / min-40℃ / min under a nitrogen atmosphere, keeping sintering for 2-10h, and cooling to room temperature to obtain the primary sintered coal.

[0019] The second-stage step temperature sintering is sintering the dried coal directly at 300-700℃ for 5-50s under a nitrogen atmosphere, or heating the dried coal to 300-700℃ at a heating rate of 50℃ / min-150℃ / min, keeping sintering for 5-50s, and cooling to room temperature to obtain the expansion-controlled coal.

[0020] The third-stage sintering is third-stage programmed temperature sintering; the third-stage programmed temperature sintering is heating the expansion-controlled coal-thermoplastic phenolic resin composite sample to 1100-1700℃ at a heating rate of 3℃ / min-30℃ / min under a nitrogen atmosphere, keeping sintering for 2-10h, and cooling to room temperature to obtain the expansion-controlled coated hard carbon material.

[0021] The phenolic compound is phenol, o-methylphenol, m-methylphenol, p-methylphenol, o-dihydroxybenzene, m-dihydroxybenzene, p-dihydroxybenzene, p-isopropylphenol, p-methylaminophenol, p-propylphenol, p-butylphenol, p-pentylphenol or p-heptylphenol.

[0022] The phenolic compound is an ether of part of the hydroxyl groups of o-dihydroxybenzene, m-dihydroxybenzene or p-dihydroxybenzene and methanol, butanol or isopropyl alcohol.

[0023] The aldehyde compound is formaldehyde, acetaldehyde, furfural, propyl aldehyde, glyoxal, glutaraldehyde or malonaldehyde.

[0024] The catalyst is one of oxalic acid, hydrochloric acid, sulfuric acid or phosphoric acid, or a mixture of any two in any ratio.

[0025] The acidic solution is a solution of sulfuric acid, hydrochloric acid or nitric acid, or an acidic mixed solution of sulfuric acid and acetic acid, propionic acid, sodium acetate, sodium sulfate or an oxidizing transition metal compound; or an acidic mixed solution of hydrochloric acid and acetic acid, propionic acid, sodium acetate or sodium sulfate; the oxidizing transition metal compound is sodium permanganate, potassium permanganate, sodium manganate, potassium manganate, sodium sulfate, potassium sulfate, sodium dichromate, sodium chromate or chromium sulfate.

[0026] The acid solution is a mixed solution of sulfuric acid with a concentration of 20 wt.%-80 wt.% and acetic acid with a concentration of 3 wt.%-30 wt.%.

[0027] The impurity-removed coal is coal powder from which iron, silicon and aluminum ions are removed.

[0028] The inert electrode is a graphite electrode, a titanium electrode or a titanium-manganese alloy electrode.

[0029] The present application has the following advantages:

[0030] 1. By electrolyzing the primary fired coal, the present application embeds the high-temperature easily-decomposable impurity ions into the interlayer of the primary fired coal microcrystal to obtain the electrolytic coal with embedded impurity ions. In a nitrogen atmosphere, during the step-up sintering process, the impurity ions embedded in the coal microcrystal will instantaneously decompose to form gas containing impurity atoms. These gases instantaneously escape from the primary fired coal microcrystal to expand the interlayer distance of the coal microcrystal structure. By controlling the amount of the embedded impurity ions in the primary fired coal microcrystal, the time and frequency of washing the electrolytic coal, the step-up sintering temperature and sintering time, etc., the interlayer distance of the coal microcrystal can be controlled. The prepared hard carbon has an interlayer distance greater than 0.37 nm, which reduces the resistance of the relatively large sodium ion embedding / dembedding, thereby significantly improving the large-current and low-temperature discharge performance of the sample.

[0031] 2. By controlling the expansion degree of the coal microcrystal, the present application expands the interlayer distance of the microcrystal, opens the nanopores in the pyrolytic coal microcrystal which are not permeable to the surface of the sample particles, and allows the in-situ formed thermoplastic phenolic resin in the later stage to permeate into the nanopores. These thermoplastic phenolic resins will block the nanopores formed in the first and second sintering processes in the third sintering process, thereby reducing the actual surface area of the sample particles. At the same time, the thermoplastic phenolic resin blocking the coal microcrystal can separate the hard carbon formed by the coal from direct contact with the electrolyte, thereby improving the coulombic efficiency of the sample and the charge-discharge cycle performance of the sample.

[0032] 3. In the third sintering process, as the sintering temperature increases, the thermoplastic phenolic resin formed in the present application will soften, thereby strengthening the effect of blocking the nanopores of the coal and improving the coulombic efficiency and cycle performance of the sample.

[0033] 4. Compared with the prior art, the present application greatly reduces the sintering temperature and sintering time for preparing the hard carbon material, thereby achieving significant energy-saving and emission-reducing effects. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is the XRD diffraction pattern of the sample prepared in Example 1 of the present application.

[0035] Figure 2is the coulombic efficiency of the charge and discharge of the sample prepared in Example 1 of the present application.

[0036] Figure 3 is the AC impedance spectrum of the sample after 2 cycles of charge and discharge. DETAILED DESCRIPTION

[0037] The present application is further illustrated below with reference to examples. The examples are only further supplement and illustration of the present application, and are not limitation of the present application.

[0038] In the examples, the impurity-removed coal is coal powder from which iron, silicon, and aluminum impurities are removed. Example 1

[0039] The method for controlling the interlayer spacing of the structure of hard carbon material by electrolytic intercalation technology comprises the following steps:

[0040] The phenol and formaldehyde are weighed according to a molar ratio of 1:0.9, the impurity-removed anthracite is weighed according to a weight ratio of 1:0.4, and a mixed solution of sulfuric acid and acetic acid with 40 wt.% sulfuric acid and 10 wt.% acetic acid is prepared.

[0041] 1) The impurity-removed anthracite is heated to 900℃ at a heating rate of 20℃ / min under a nitrogen atmosphere, and is kept sintering for 3h, and is cooled to room temperature to prepare a primary sintered coal;

[0042] 2) The primary sintered coal is used as an anode, and a graphite electrode is used as a cathode in the mixed solution of sulfuric acid and acetic acid, and is electrolyzed at a current density of 5mA / cm 2 for 1h to prepare an electrolytic coal;

[0043] 3) The electrolytic coal is washed and vacuum dried to prepare a dried coal;

[0044] 4) The dried coal is directly sintered at 350℃ for 20s under a nitrogen atmosphere, and is cooled to room temperature to prepare a coal with controlled expansion degree;

[0045] 5) The coal with controlled expansion degree is added into a reaction kettle, and the weighed phenol and formaldehyde are mixed, and heated to 90℃, and 0.3wt.% of oxalic acid based on the weight of the phenol is added, and is kept for 4h to prepare a composite sample of the coal with controlled expansion degree and thermoplastic phenolic resin;

[0046] 6) The composite sample of the coal with controlled expansion degree and thermoplastic phenolic resin is heated to 1300℃ at a heating rate of 10℃ / min under a nitrogen atmosphere, and is kept for 5h, and is cooled to room temperature to prepare a hard carbon material coated with the coal with controlled expansion degree.

[0047] Figure 1 is the XRD diffraction pattern of the sample prepared in Example 1. Figure 1The prepared sample has structural characteristics of hard carbon.

[0048] Figure 2 is the coulombic efficiency of charge and discharge of the sample prepared in Example 1. Figure 2 The curve of the coulombic efficiency of charge and discharge versus cycle number of the sample prepared in Example 1 shows that the prepared sample maintains a coulombic efficiency of charge and discharge close to 100% at different currents.

[0049] Figure 3 is the AC impedance spectrum of the sample after 2 cycles of charge and discharge. Figure 3 The impedance test of the sample after 2 cycles of charge and discharge shows that the sample has low charge transfer impedance and surface impedance. Example 2

[0050] The method for controlling the interlayer spacing of the structure of the hard carbon material by electrolytic intercalation technology comprises the following steps:

[0051] The hydroquinone and acetaldehyde are weighed according to a molar ratio of 1:0.95, the impurity-removed coal is weighed according to a weight ratio of 1:2.2, and a mixed solution of sulfuric acid and acetic acid with a weight percentage of 80% sulfuric acid and 30% acetic acid is prepared.

[0052] 1) The impurity-removed coal is heated to 1100°C at a heating rate of 40°C / min under a nitrogen atmosphere, and sintered for 10 hours, and then cooled to room temperature to obtain a primary sintered coal;

[0053] 2) The primary sintered coal is used as an anode, and a titanium electrode is used as a cathode in the mixed solution of sulfuric acid and acetic acid, and electrolysis is performed at a current density of 50 mA / cm 2 for 6 hours to obtain an electrolytic coal;

[0054] 3) The electrolytic coal is washed and vacuum dried to obtain a dried coal;

[0055] 4) The dried coal is directly sintered at 700°C for 50 seconds in a nitrogen atmosphere, and then cooled to room temperature to obtain a controlled expansion coal;

[0056] 5) The controlled expansion coal is added into a reaction kettle, and then mixed with weighed hydroquinone and acetaldehyde, heated to 98°C, and then 5% of a hydrochloric acid catalyst by weight of the hydroquinone is added, and then the mixture is kept for 10 hours to obtain a composite sample of the controlled expansion coal-thermoplastic phenolic resin;

[0057] 6) The composite sample of the controlled expansion coal-thermoplastic phenolic resin is heated to 1700°C at a heating rate of 30°C / min in a nitrogen atmosphere, and then kept for 10 hours, and then cooled to room temperature to obtain a controlled expansion coated hard carbon material. Example 3

[0058] A method for controlling the interlayer spacing of hard carbon material structure by electrolytic intercalation technology, comprising the following steps:

[0059] The p-cresol and propyl aldehyde are weighed according to a molar ratio of 1:0.2; the impurity-removed coal is weighed according to a weight ratio of 1:0.3; and a mixed solution of sulfuric acid and acetic acid is prepared, with 20 wt.% sulfuric acid and 3 wt.% acetic acid.

[0060] 1) The impurity-removed coal is heated to 750°C at a heating rate of 15°C / min under a nitrogen atmosphere, and sintered for 2 h, and then cooled to room temperature to obtain a primary sintered coal;

[0061] 2) The primary sintered coal is used as an anode, and a titanium-manganese alloy electrode is used as a cathode in a mixed solution of sulfuric acid and acetic acid, and electrolysis is performed at a current density of 20 mA / cm 2 for 6 h to obtain an electrolytic coal;

[0062] 3) The electrolytic coal is washed and vacuum dried to obtain a dried coal;

[0063] 4) The dried coal is directly sintered at 600°C for 5 s in a nitrogen atmosphere, and then cooled to room temperature to obtain a coal with controlled expansion degree;

[0064] 5) The coal with controlled expansion degree is added into a reaction kettle, and then mixed with weighed p-cresol and propyl aldehyde, heated to 80°C, and then 5 wt.% of sulfuric acid catalyst based on the weight of p-cresol is added, and then incubated for 10 h to obtain a composite sample of coal with controlled expansion degree and thermoplastic phenolic resin;

[0065] 6) The composite sample of coal with controlled expansion degree and thermoplastic phenolic resin is heated to 1100°C at a heating rate of 3°C / min in a nitrogen atmosphere, and then incubated for 2 h, and then cooled to room temperature to obtain a hard carbon material coated with coal with controlled expansion degree. Example 4

[0066] A method for controlling the interlayer spacing of hard carbon material structure by electrolytic intercalation technology, comprising the following steps:

[0067] The catechol and acetaldehyde are weighed according to a molar ratio of 1:0.6; the impurity-removed coal is weighed according to a weight ratio of 1:1; and a mixed solution of sulfuric acid and sodium permanganate is prepared, with 20 wt.% sulfuric acid and 0.1% sodium permanganate.

[0068] 1) The impurity-removed coal is heated to 750°C at a heating rate of 25°C / min under a nitrogen atmosphere, and sintered for 10 h, and then cooled to room temperature to obtain a primary sintered coal;

[0069] 2) Electrolysis of the prepared coal in a mixed solution of sulfuric acid and sodium hypochlorite with a graphite electrode as cathode and the prepared coal as anode at 10 mA / cm 2 current density for 1 h to obtain electrolytic coal;

[0070] 3) Washing and drying the electrolytic coal to obtain dried coal;

[0071] 4) Directly sintering the dried coal at 700 °C for 5 s in a nitrogen atmosphere, and cooling to room temperature to obtain coal with controlled expansion degree;

[0072] 5) In a reaction kettle, nitrogen was introduced, and coal with controlled expansion degree was added, and then a weighed amount of catechol and acetaldehyde was mixed, heated to 80 °C, and a hydrochloric acid catalyst with a weight of 1 wt.% of the weight of catechol was added, and incubated for 5 h to obtain a composite sample of coal with controlled expansion degree-thermoplastic phenolic resin;

[0073] 6) In a nitrogen atmosphere, the composite sample of coal with controlled expansion degree-thermoplastic phenolic resin was heated to 1500 °C at a heating rate of 15 °C / min, incubated for 5 h, and cooled to room temperature to obtain a coated hard carbon material with controlled expansion degree. Example 5

[0074] A method for controlling the interlayer spacing of the structure of hard carbon material by electrolytic embedding technology, comprising the following steps:

[0075] According to the molar ratio of 10% hydroxymethyl butyl ether of catechol to acetaldehyde of 1:0.5, 10% hydroxymethyl butyl ether of catechol was weighed, and according to the weight ratio of impurity-removed coal to 10% hydroxymethyl butyl ether of catechol of 1:0.8, impurity-removed coal was weighed, and a mixed solution of sulfuric acid and sodium acetate with 80 wt.% sulfuric acid and 3 wt.% sodium acetate was prepared.

[0076] 1) In a nitrogen atmosphere, the impurity-removed coal was heated to 950 °C at a heating rate of 15 °C / min, incubated for 5 h, and cooled to room temperature to obtain a coal;

[0077] 2) Electrolysis of the prepared coal in a mixed solution of sulfuric acid and sodium acetate with a graphite electrode as cathode and the prepared coal as anode at 5 mA / cm 2 current density for 0.5 h to obtain electrolytic coal;

[0078] 3) Washing and drying the electrolytic coal to obtain dried coal;

[0079] 4) Directly sintering the dried coal at 300 °C for 50 s in a nitrogen atmosphere, and cooling to room temperature to obtain coal with controlled expansion degree;

[0080] 5) In a reaction kettle, nitrogen was introduced, and the controlled swelling degree coal was added, and then the weighed 10% hydroxymethyl ether of hydroquinone and butanol and acetaldehyde were mixed, heated to 88°C, and then the weighed 2wt.% oxalic acid catalyst of 10% hydroxymethyl ether of hydroquinone and butanol was added, and the temperature was kept for 3h, to prepare the controlled swelling degree coal-thermoplastic phenolic resin composite sample;

[0081] 6) In a nitrogen atmosphere, the controlled swelling degree coal-thermoplastic phenolic resin composite sample was heated to 1200°C at a heating rate of 3°C / min, and kept for 10h; cooled to room temperature, to prepare the controlled swelling degree coated hard carbon material. Example 6

[0082] The method for controlling the interlayer spacing of the hard carbon material structure by electrolytic intercalation technology comprises the following steps:

[0083] The p-cresol and furfural were weighed according to the molar ratio of 1:0.9; the impurity-removed coal was weighed according to the weight ratio of 1:2.2; and a mixed solution of sulfuric acid and acetic acid was prepared, wherein the sulfuric acid was 60wt.% and the acetic acid was 15wt.%.

[0084] 1) In a nitrogen atmosphere, the impurity-removed coal was heated to 950°C at a heating rate of 30°C / min, and kept for 8h; cooled to room temperature, to prepare the initial sintered coal;

[0085] 2) In the mixed solution of sulfuric acid and acetic acid, the prepared initial sintered coal was used as the anode, and the graphite electrode was used as the cathode, and electrolysis was carried out at a current density of 30mA / cm 2 for 3h, to prepare the electrolytic coal;

[0086] 3) The electrolytic coal was washed and vacuum dried, to prepare the dried coal;

[0087] 4) In a nitrogen atmosphere, the dried coal was directly sintered at 600°C for 50s, and then cooled to room temperature, to prepare the controlled swelling degree coal;

[0088] 5) In a reaction kettle, nitrogen was introduced, and the controlled swelling degree coal was added, and then the weighed p-cresol and furfural were mixed, and stirred and mixed, and heated to 95°C; and then the weighed 1wt.% mixture of oxalic acid and hydrochloric acid with a molar ratio of 1:1 was added, and kept for 10h, to prepare the controlled swelling degree coal-thermoplastic phenolic resin composite sample;

[0089] 6) In a nitrogen atmosphere, the controlled swelling degree coal-thermoplastic phenolic resin composite sample was heated to 1300°C at a heating rate of 8°C / min, and kept for 10h, and then cooled to room temperature, to prepare the controlled swelling degree coated hard carbon material. Example 7

[0090] A method for controlling the interlayer spacing of a hard carbon material structure by electrolytic intercalation technology, comprising the following steps:

[0091] According to the molar ratio of p-cresol to propyl aldehyde 1:0.95, p-cresol and propyl aldehyde are weighed; according to the weight ratio of impurity-removed coal to p-cresol 1:0.85, impurity-removed coal is weighed; a mixed solution of sulfuric acid and chromium sulfate with 50 wt.% sulfuric acid and 0.5 wt.% chromium sulfate is prepared.

[0092] 1) Under a nitrogen atmosphere, the impurity-removed coal is heated to 1000℃ at a heating rate of 20℃ / min, and sintered for 8h, and then cooled to room temperature to obtain a primary sintered coal;

[0093] 2) In the mixed solution of sulfuric acid and chromium sulfate, a graphite electrode is used as the cathode, and the prepared primary sintered coal is used as the anode, and electrolysis is carried out at a current density of 20mA / cm 2 for 1h to obtain an electrolytic coal;

[0094] 3) The electrolytic coal is washed and vacuum dried to obtain a dried coal;

[0095] 4) In a nitrogen atmosphere, the dried coal is heated to 500℃ at a heating rate of 100℃ / min, and sintered for 40s at the temperature, and then cooled to room temperature to obtain a controlled expansion coal;

[0096] 5) In a reaction kettle, nitrogen is introduced, the controlled expansion coal is added, and then a weighed amount of p-cresol and propyl aldehyde is mixed, and heated to 98℃; 1wt.% of sulfuric acid based on the weight of p-cresol is added, and the temperature is maintained for 3h to obtain a controlled expansion coal-thermoplastic phenolic resin composite sample;

[0097] 6) In a nitrogen atmosphere, the controlled expansion coal-thermoplastic phenolic resin composite sample is heated to 1700℃ at a heating rate of 30℃ / min, and sintered for 9h; and then cooled to room temperature to obtain a controlled expansion coated hard carbon material.

Claims

1. A method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology, characterized in that, Includes the following steps: 1) Under a nitrogen atmosphere, the impurity-removed coal is subjected to the first stage of sintering to obtain primary calcined coal; 2) In an acidic solution, using an inert electrode as the cathode and virgin coal as the anode, at a current of 2–50 mA / cm². 2 Electrolytic coal is obtained by electrolysis at a current density for 0.5–6 hours. 3) Wash and dry the electrolytic coal to obtain dry coal; 4) In a nitrogen atmosphere, dry coal is subjected to a second-stage step temperature rise sintering to obtain coal with controlled expansion. The second-stage step temperature rise sintering is carried out by directly placing the dry coal in a nitrogen atmosphere at 300-700℃ for 5-50s, or heating the dry coal to 300-700℃ at a heating rate of 50℃ / min-150℃ / min, holding the temperature for sintering for 5-50s, and then cooling to room temperature to obtain coal with controlled expansion. 5) Nitrogen gas is introduced into the reactor, coal with controlled expansion is added, and then weighed phenolic compounds and aldehyde compounds are mixed in; the mixture is stirred continuously and heated to 80-98℃; 0.1wt.%-5wt.% of catalyst of phenolic compounds is added, and the mixture is kept at this temperature for 3-10 hours to obtain a composite sample of coal with controlled expansion and thermoplastic phenolic resin. 6) In a nitrogen atmosphere, the composite sample of coal-thermoplastic phenolic resin with controlled expansion is subjected to a third-stage sintering to obtain a hard carbon material with controlled expansion.

2. The method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology according to claim 1, characterized in that, The molar ratio of the phenolic compound to the aldehyde compound is 1:0.2 to 0.95; the weight ratio of the purified coal to the phenolic compound is 1:0.3 to 2.

2.

3. The method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology according to claim 1, characterized in that, The first stage of sintering is the first stage of programmed temperature rise sintering; the first stage of programmed temperature rise sintering is to heat the impurity-removed coal to 750-1100℃ at a heating rate of 15℃ / min to 40℃ / min under a nitrogen atmosphere, hold it at that temperature for 2-10 hours, and then cool it to room temperature to obtain the initial calcined coal.

4. The method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology according to claim 1, characterized in that, The third stage of sintering is a third stage of programmed temperature rise sintering; the third stage of programmed temperature rise sintering is to heat the composite sample of coal-thermoplastic phenolic resin with controlled expansion to 1100-1700℃ in a nitrogen atmosphere at a heating rate of 3℃ / min to 30℃ / min, hold for 2-10h, and cool to room temperature to obtain a hard carbon material with controlled expansion.

5. The method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology according to claim 1, characterized in that, The phenolic compounds mentioned are phenol, o-methylphenol, m-methylphenol, p-methylphenol, catechol, resorcinol, hydroquinone, p-isopropylphenol, p-methylaminophenol, p-propylphenol, p-butylphenol, p-pentylphenol, or p-heptylphenol; Alternatively, the phenolic compound is an etherification of some of the hydroxyl groups of catechol, resorcinol, or hydroquinone with methanol, butanol, or isopropanol.

6. The method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology according to claim 1, characterized in that, The aldehyde compound is formaldehyde, acetaldehyde, furfural, propionaldehyde, glyoxal, glutaraldehyde, or malondialdehyde; the catalyst is one or a mixture of two of oxalic acid, hydrochloric acid, sulfuric acid, or phosphoric acid in any proportion.

7. The method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology according to claim 1, characterized in that, The acidic solution is a solution of sulfuric acid, hydrochloric acid, or nitric acid, or an acidic mixed solution of sulfuric acid with acetic acid, propionic acid, sodium acetate, sodium sulfate, or an oxidizing transition metal compound; Or an acidic mixed solution of hydrochloric acid with acetic acid, propionic acid, sodium acetate or sodium sulfate; the oxidizing transition metal compound is sodium permanganate, potassium permanganate, sodium manganate, potassium manganate, sodium sulfate, potassium sulfate, sodium dichromate, sodium chromate or chromium sulfate.

8. The method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology according to claim 1, characterized in that, The acidic solution is a mixture of sulfuric acid with a concentration of 20 wt.% to 80 wt.% and acetic acid with a concentration of 3 wt.% to 30 wt.%.

9. The method for controlling the interlayer spacing of hard carbon materials using electrolytic intercalation technology according to claim 1, characterized in that, The impurity-removed coal is coal powder with iron, silicon, and aluminum impurities removed; the inert electrode is a graphite, titanium, or titanium-manganese alloy electrode.

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