Method for preparing biomass-based hard carbon through in-situ continuous catalytic carbonization and application

Abstract

The invention discloses a method for preparing biomass-based hard carbon through in-situ continuous catalytic carbonization and application, and belongs to the technical field of biomass-based carbon material preparation and energy storage. The method comprises the following steps: mixing a biomass raw material with a zinc salt aqueous solution; performing low-temperature pyrolysis and carbonization on the mixed material in an inert atmosphere; performing high-temperature carbonization on the low-temperature pyrolysis carbonization intermediate in an inert atmosphere; and after high-temperature carbonization is finished, naturally cooling to room temperature, washing and drying to obtain the hard carbon material. By utilizing the differentiated existence forms of the zinc salt at different temperatures and the characteristics of in-situ continuous catalysis and high-temperature volatilization, special rapid heating equipment is not needed, and the catalyst does not need to be washed off after low-temperature pyrolysis carbonization, so that the cooperative regulation and control of the interlayer spacing and the closed-pore structure of the biomass-based hard carbon microcrystalline are realized; the biomass-based hard carbon with wide microcrystalline interlayer spacing and rich closed pore structures is obtained. The obtained hard carbon has large reversible specific capacitance, high platform capacity and high rate performance when being applied to a sodium / lithium ion battery negative electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biomass-based carbon material preparation and energy storage, and particularly relates to a method for preparing biomass-based hard carbon through in-situ continuous catalytic carbonization and application thereof. BACKGROUND

[0002] Energy storage is an important guarantee for national energy security, an essential infrastructure for new energy development, and a driving force for the development of emerging industries such as electric vehicles. Sodium-ion batteries have advantages such as abundant sodium resources, low cost, excellent fast-charging and low-temperature performance, and are considered as the preferred choice for the next generation of efficient energy storage systems. The negative electrode material is the key to the commercialization process of sodium-ion batteries. Biomass-based hard carbon has advantages such as excellent comprehensive sodium storage performance, abundant and renewable raw materials, and low cost, and is the most potential negative electrode material in the practicalization process of sodium-ion batteries.

[0003] Biomass-based hard carbon is generally prepared by pyrolysis carbonization of biomass under an inert atmosphere. The biomass-based hard carbon prepared by conventional methods generally has defects such as narrow microcrystalline layer spacing (d 002 ) and few closed pores, and has disadvantages such as small specific capacity and poor rate performance when used as a negative electrode material for sodium-ion batteries. In order to increase the microcrystalline layer spacing of hard carbon, the commonly used methods are: 1) reducing the carbonization temperature (<1000℃); 2) using a joule heat rapid heating device, etc. In order to increase the number of closed pores of hard carbon, the commonly used methods are: 1) increasing the carbonization temperature (>1400℃); 2) adding activating reagents to create pores during the low-temperature pyrolysis stage (<800℃), etc. However, these methods only target one of the microcrystalline layer spacing and closed pores, and often have to give up something to get something, making it difficult to achieve the synergistic control of the microcrystalline layer spacing and closed pores of hard carbon. For example, high carbonization temperature can reduce the microcrystalline spacing, but is beneficial to the formation of closed pores, and low carbonization temperature is beneficial to maintaining large microcrystalline layer spacing, but is not conducive to the formation of closed pores; adding chemical reagents to create pores during the low-temperature carbonization stage can achieve the richness of closed pores, but it is difficult to inhibit the shrinkage of the layer spacing during the high-temperature carbonization stage, and the washing of the activating reagents also increases the additional operation steps and comprehensive cost; joule heat rapid heating carbonization can obtain a wide hard carbon microcrystalline layer spacing, but it is difficult to form closed pores, and there is currently a lack of engineering application equipment and prospects. SUMMARY

[0004] To solve the above problems in the prior art, the technical problems to be solved by the present application are to provide a method for preparing biomass-based hard carbon by in-situ continuous catalytic carbonization, which utilizes the differential existence forms of zinc salt at different temperatures and the in-situ continuous catalytic effect, and the characteristics of high-temperature volatilization, without the need for special rapid heating equipment, and without the need for washing and removing the catalyst after low-temperature pyrolysis carbonization, to prepare biomass-based hard carbon with wide microcrystalline interlayer spacing and rich closed pore structure, to realize the synergistic regulation of the microcrystalline interlayer spacing and the closed pore structure of the biomass-based hard carbon, and to solve the problems of the conventional regulation method of the microstructure of hard carbon, such as the trade-off between the two, the difficulty in synergistic regulation, the complicated operation steps, the need for special rapid heating equipment, and the difficulty in engineering application. Another technical problem to be solved by the present application is to provide an application of biomass-based hard carbon in sodium ion batteries and / or lithium ion batteries, and the obtained hard carbon has large reversible specific capacitance, high platform capacity and high rate performance when applied to the negative electrode material of the sodium ion battery.

[0005] To solve the above problems, the technical solutions adopted by the present application are as follows:

[0006] A method for preparing biomass-based hard carbon by in-situ continuous catalytic carbonization, wherein biomass raw materials and a zinc salt aqueous solution are mixed, the mixture is subjected to low-temperature pyrolysis carbonization under an inert atmosphere, the low-temperature pyrolysis carbonization intermediate is subjected to high-temperature carbonization under an inert atmosphere, and the high-temperature carbonization is naturally cooled to room temperature after completion, and then the hard carbon material is obtained after washing and drying.

[0007] In the method for preparing biomass-based hard carbon by in-situ continuous catalytic carbonization, the biomass raw materials are one or more of lignin, cellulose, wood / bamboo chips or fruit shells; the zinc salt is one or more of zinc chloride, zinc acetate or zinc sulfate; preferably, the zinc salt is zinc chloride.

[0008] In the method for preparing biomass-based hard carbon by in-situ continuous catalytic carbonization, after the biomass raw materials and the zinc salt aqueous solution are mixed, the mixture is placed at 100-150 DEG C for 1-3 h; preferably, the mixture is placed at 140 DEG C for 2 h.

[0009] In the method for preparing biomass-based hard carbon by in-situ continuous catalytic carbonization, the mass ratio of the biomass raw materials to the zinc salt is 1:0.1-1:1; preferably, the mass ratio is 1:0.3-1:0.4; further preferably, the mass ratio is 1:0.35.

[0010] In the method for preparing biomass-based hard carbon by in-situ continuous catalytic carbonization, under a nitrogen or argon atmosphere, the mixture is heated to 400-800 DEG C at a heating rate of 1-20 DEG C / min, and is kept at the temperature for 1-3 h; preferably, the heating rate is 5 DEG C / min, the pyrolysis carbonization temperature is 600 DEG C, and the keeping time is 2 h.

[0011] The method for preparing the biomass-based hard carbon by in-situ continuous catalytic carbonization comprises the following steps: under the atmosphere of nitrogen or argon, carbonization intermediates are pyrolyzed and carbonized at a temperature rising rate of 1-20℃ / min to 1000-1600℃, and are kept for 1-4h; preferably, the temperature rising rate is 2℃ / min, the high-temperature carbonization temperature is 1300℃, and the keeping time is 2h.

[0012] The method for preparing the biomass-based hard carbon by in-situ continuous catalytic carbonization, after the carbonization is completed, the hard carbon is washed with 0.1M hydrochloric acid at 100℃ for three times, and then is washed with deionized water at 20-100℃ until the pH is 6-7, and is dried at 120℃ for 4h.

[0013] The biomass-based hard carbon material prepared by the above method.

[0014] The biomass-based hard carbon material is applied to sodium ion batteries and / or lithium ion batteries.

[0015] Compared with the prior art, the method has the following beneficial effects:

[0016] (1) Without special rapid heating equipment and without washing and removing the catalyst after low-temperature pyrolytic carbonization, the method can realize the synergistic regulation of the interlayer spacing of the hard carbon microcrystal and the closed pore structure by utilizing the differential existence form of the zinc salt at different temperatures and the in-situ continuous catalytic effect, and the characteristics of high-temperature volatilization, and can obtain the hard carbon material with wide interlayer spacing of the hard carbon microcrystal and rich closed pore structure, thereby solving the problems of the conventional regulation method of the hard carbon microstructure, such as the trade-off, the difficulty in synergy, the complicated operation steps, the need for special rapid heating equipment, and the difficulty in engineering application.

[0017] (2) When the biomass-based hard carbon is applied to the negative electrode material of the sodium ion battery, the biomass-based hard carbon has large reversible specific capacity, high platform capacity and high rate performance.

[0018] (3) The method has the advantages of simple operation, obvious effect and strong applicability. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The XRD pattern of the hard carbon of Comparative Examples 1-3;

[0020] Figure 2 The XRD pattern of the hard carbon of Comparative Example 2 and Examples 1-3;

[0021] Figure 3 The SAXS pattern of the hard carbon of Comparative Example 2 and Examples 1-3;

[0022] Figure 4 The SAXS pattern of the hard carbon of Comparative Example 4 and Example 4;

[0023] Figure 5Galvanostatic charge-discharge curves of Comparative Example 1 and Examples 1-4 as negative electrode for sodium ion batteries;

[0024] Figure 6 In-situ XRD patterns of Example 3 at different temperatures during preparation. DETAILED DESCRIPTION

[0025] The application will be further described in conjunction with specific examples.

[0026] Comparative Example 1

[0027] 5 g of lignin was added with 100 mL of deionized water, and kept at 140°C for 2 h, and then transferred to a tube furnace, and heated to 600°C at a heating rate of 5°C / min under nitrogen atmosphere, and kept for 2 h; heated to 900°C at a heating rate of 2°C / min, and kept for 2 h; after natural cooling to room temperature, washed with 0.1 M hydrochloric acid at 100°C for three times, and then washed with deionized water at room temperature until the pH was 6-7, and dried at 120°C for 4 h to obtain hard carbon HC-C1.

[0028] Comparative Example 2

[0029] 5 g of lignin was added with 100 mL of deionized water, and kept at 140°C for 2 h, and then transferred to a tube furnace, and heated to 600°C at a heating rate of 5°C / min under nitrogen atmosphere, and kept for 2 h; heated to 1300°C at a heating rate of 2°C / min, and kept for 2 h; after natural cooling to room temperature, washed with 0.1 M hydrochloric acid at 100°C for three times, and then washed with deionized water at room temperature until the pH was 6-7, and dried at 120°C for 4 h to obtain hard carbon HC-C2.

[0030] Comparative Example 3

[0031] 5 g of lignin was added with 100 mL of deionized water, and kept at 140°C for 2 h, and then transferred to a tube furnace, and heated to 600°C at a heating rate of 5°C / min under nitrogen atmosphere, and kept for 2 h; heated to 1600°C at a heating rate of 2°C / min, and kept for 2 h; after natural cooling to room temperature, washed with 0.1 M hydrochloric acid at 100°C for three times, and then washed with deionized water at room temperature until the pH was 6-7, and dried at 120°C for 4 h to obtain hard carbon HC-C3.

[0032] Comparative Example 4

[0033] 5g bamboo chips were added with 100 mL deionized water dissolving 2.0 g of phosphoric acid, and kept at 140 °C for 2 h, then transferred to a tube furnace, and heated to 600 °C at a heating rate of 5 °C / min under nitrogen atmosphere, and kept for 2 h; the obtained carbonized material was washed with deionized water at 100 °C until pH 6-7, and dried at 140 °C for 4 h; the dried carbonized material was heated to 1300 °C at a heating rate of 2 °C / min, and kept for 2 h; after natural cooling to room temperature, washed with 0.1 M hydrochloric acid at 100 °C for three times, then washed with deionized water at room temperature until pH 6-7, and dried at 120 °C for 4 h to obtain hard carbon HC-C4.

[0034] Example 1

[0035] 5g bamboo chips were added with 100 mL deionized water dissolving 2.0 g of phosphoric acid, and kept at 140 °C for 2 h, then transferred to a tube furnace, and heated to 600 °C at a heating rate of 5 °C / min under nitrogen atmosphere, and kept for 2 h; the obtained carbonized material was washed with deionized water at 100 °C until pH 6-7, and dried at 140 °C for 4 h; the dried carbonized material was heated to 1300 °C at a heating rate of 2 °C / min, and kept for 2 h; after natural cooling to room temperature, washed with 0.1 M hydrochloric acid at 100 °C for three times, then washed with deionized water at room temperature until pH 6-7, and dried at 120 °C for 4 h to obtain hard carbon HC-C4.

[0036] Example 2

[0037] 5g bamboo chips were added with 100 mL deionized water dissolving 2.0 g of phosphoric acid, and kept at 140 °C for 2 h, then transferred to a tube furnace, and heated to 600 °C at a heating rate of 5 °C / min under nitrogen atmosphere, and kept for 2 h; the obtained carbonized material was washed with deionized water at 100 °C until pH 6-7, and dried at 140 °C for 4 h; the dried carbonized material was heated to 1300 °C at a heating rate of 2 °C / min, and kept for 2 h; after natural cooling to room temperature, washed with 0.1 M hydrochloric acid at 100 °C for three times, then washed with deionized water at room temperature until pH 6-7, and dried at 120 °C for 4 h to obtain hard carbon HC-C4.

[0038] Example 3

[0039] 5g bamboo chips were added with 100 mL deionized water dissolving 2.0 g of phosphoric acid, and kept at 140 °C for 2 h, then transferred to a tube furnace, and heated to 600 °C at a heating rate of 5 °C / min under nitrogen atmosphere, and kept for 2 h; the obtained carbonized material was washed with deionized water at 100 °C until pH 6-7, and dried at 140 °C for 4 h; the dried carbonized material was heated to 1300 °C at a heating rate of 2 °C / min, and kept for 2 h; after natural cooling to room temperature, washed with 0.1 M hydrochloric acid at 100 °C for three times, then washed with deionized water at room temperature until pH 6-7, and dried at 120 °C for 4 h to obtain hard carbon HC-C4.

[0040] Example 4

[0041] 5g bamboo chips were added with 100 mL deionized water dissolving 1.75 g zinc acetate, and kept at 140 °C for 2 h, then transferred into a tube furnace, and heated to 600 °C at a heating rate of 5 °C / min under nitrogen atmosphere, and kept for 2 h; heated to 1300 °C at a heating rate of 2 °C / min, and kept for 2 h; after naturally cooling to room temperature, washed with 0.1 M hydrochloric acid at 100 °C for three times, then washed with deionized water at room temperature until the pH was 6-7, and dried at 120 °C for 4 h to obtain hard carbon HC-4.

[0042] Table 1 Microcrystalline layer spacing, closed pore volume, specific capacitance, platform capacity and rate performance of Comparative Example 1 and Examples 1-4

[0043]

[0044] a Microcrystalline layer spacing was calculated according to X-ray diffraction (XRD) d 002 The crystal plane data were calculated;

[0045] b Closed pore volume was calculated according to small-angle X-ray scattering (SAXS) data;

[0046] c The test current density was 0.05 A / g;

[0047] d The rate performance refers to the ratio of the specific capacitance measured at 1.0 A / g to the specific capacitance measured at 0.05 A / g.

[0048] As can be seen from Comparative Examples 1-3, simply adjusting the carbonization temperature can only optimize one of the microcrystalline layer spacing or the closed pore volume, and since there is a trade-off relationship between these two properties of hard carbon (one increases and the other decreases), it is difficult to synergistically control them by adjusting the conventional carbonization temperature.

[0049] As can be seen from Comparative Example 4, the activation pore-making in the low-temperature pyrolysis carbonization stage can significantly improve the closed pore volume, but the effect of expanding the microcrystalline layer spacing is not obvious.

[0050] As can be seen from Comparative Examples 1-4, the conventional control method is difficult to achieve the synergistic optimization of the microcrystalline layer spacing and the closed pore structure, and the consideration of the specific capacitance and the rate performance of the hard carbon.

[0051] As can be seen from Examples 1-4, the zinc salt-mediated continuous catalytic carbonization can maintain or even expand the microcrystalline layer spacing and enrich the closed pores, and obtain hard carbon with high specific capacitance, high platform capacity and high rate performance.

[0052] From Examples 1-3, the hard carbon prepared in Example 2 has the widest interlayer spacing of crystallites, the largest closed pore capacity, the highest specific capacitance and the best rate performance. Too little (Example 1) zinc chloride causes insufficient closed pore formation, and too much (Example 3) zinc chloride causes over-activation and the resulting large pores are difficult to convert into closed pores.

[0053] From Example 4, it can be seen that zinc acetate also has the effect of in-situ continuous catalytic carbonization, but is not as good as zinc chloride. Figure 1 As the carbonization temperature increases, the d 002 peak shifts to the right, indicating that the interlayer spacing of the crystal lattice gradually decreases.

[0054] From Example 4, it can be seen that zinc acetate also has the effect of in-situ continuous catalytic carbonization, but is not as good as zinc chloride. Figure 2 The results show that the addition of zinc chloride promotes the hard carbon to have a smaller d 002 peak, indicating that the interlayer spacing of the crystal lattice is larger, and as the amount of zinc chloride added increases, the d 002 peak shifts to the left at a greater amplitude, indicating that the interlayer spacing of the crystal lattice is larger.

[0055] From Example 4, it can be seen that zinc acetate also has the effect of in-situ continuous catalytic carbonization, but is not as good as zinc chloride. Figure 3 The results show that the addition of zinc chloride promotes the hard carbon to have a larger shoulder peak in the 0.1-1 angstrom 1 range of small-angle X-ray scattering, indicating an increase in closed pore capacity, and as the amount of zinc chloride added increases, the shoulder peak first increases and then decreases, with the shoulder peak of the hard carbon prepared in Example 2 being the largest, indicating that it has the largest closed pore capacity.

[0056] From Example 4, it can be seen that zinc acetate also has the effect of in-situ continuous catalytic carbonization, but is not as good as zinc chloride. Figure 4 The results show that the hard carbon prepared by phosphoric acid and zinc acetate activation both have shoulder peaks in the 0.1-1 angstrom -1 range of small-angle X-ray scattering, indicating that they both have abundant closed pores.

[0057] From Example 4, it can be seen that zinc acetate also has the effect of in-situ continuous catalytic carbonization, but is not as good as zinc chloride. Figure 5 The results show that the specific capacitance of the prepared hard carbon is in the order of Example 2 > Example 4 > Example 3 > Example 1 > Comparative Example 1, which is consistent with the results of the interlayer spacing of the crystallites and the closed pore structure.

[0058] From Example 4, it can be seen that zinc acetate also has the effect of in-situ continuous catalytic carbonization, but is not as good as zinc chloride. Figure 6 The mechanism of in-situ continuous catalytic carbonization is as follows: in the temperature range from room temperature to 600°C, the zinc salt mainly exists in the form of zinc chloride, which is the mechanism of catalyzing aromaticization and catalyzing selective bond breaking; from 600°C to 900°C, the zinc salt mainly exists in the form of ZnO and Zn element, which is the mechanism of etching pore formation and catalyzing crystallite growth; after 900°C, the zinc salt mainly exists in the form of Zn element, and since Zn starts to volatilize at 907°C, the main functions in this stage are to support the carbon layer (to prevent the carbon layer from shrinking), to catalyze graphitization, and to promote the carbon layer to form closed pores.

Claims

1. A method for producing a biomass-based hard carbon by in-situ continuous catalytic carbonization, characterized by, Mixing biomass raw material and zinc salt aqueous solution; pyrolysis carbonization of the mixture at low temperature under inert atmosphere; high temperature carbonization of the low temperature pyrolysis carbonization intermediate under inert atmosphere; natural cooling to room temperature after high temperature carbonization; washing and drying to obtain hard carbon material.

2. The method of claim 1, wherein the in-situ continuous catalytic carbonization of biomass for producing hard carbon is characterized by, The biomass raw material is one or more of lignin, cellulose, wood / bamboo chips or fruit shell; the zinc salt is one or more of zinc chloride, zinc acetate or zinc sulfate.

3. The method of claim 1, wherein the in-situ continuous catalytic carbonization of biomass to produce hard carbon is characterized by, After mixing biomass raw material and zinc salt aqueous solution, the mixture is placed at 100-150℃ for 1-3h.

4. The method of claim 1, wherein the in-situ continuous catalytic carbonization of biomass to produce hard carbon is characterized by, The mass ratio of biomass raw material to zinc salt is 1:0.1-1:

1.

5. The method of claim 1, wherein the in-situ continuous catalytic carbonization of biomass to produce hard carbon is characterized by, The mixture is heated to 400-800℃ at a heating rate of 1-20℃ / min under nitrogen or argon atmosphere, and is kept at the temperature for 1-3h.

6. The method of claim 1, wherein the in-situ continuous catalytic carbonization of biomass to produce hard carbon is characterized by, The low temperature pyrolysis carbonization intermediate is heated to 1000-1600℃ at a heating rate of 1-20℃ / min under nitrogen or argon atmosphere, and is kept at the temperature for 1-4h.

7. The method of claim 1, wherein the in-situ continuous catalytic carbonization of biomass to produce hard carbon is characterized by, After carbonization, the mixture is washed with 0.1M hydrochloric acid at 100℃ for three times, then washed with deionized water at 20-100℃ until pH is 6-7, and dried at 120℃ for 4h.

8. Biomass-based hard carbon material prepared by the method of any one of claims 1-7.

9. Use of the biomass-based hard carbon material of claim 8 in sodium ion battery and / or lithium ion battery.

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