Lignocellulose biomass-based hard carbon negative electrode material and preparation method and application thereof

Abstract

The invention discloses a lignocellulose biomass-based hard carbon negative electrode material as well as a preparation method and application thereof. The method comprises the following steps: carrying out hydrothermal pretreatment on lignocellulose biomass by using low-corrosivity maleic acid, and regulating and controlling the composition of the lignocellulose biomass, the maleic acid and the lignocellulose to obtain a precursor rich in lignin and cellulose; in the pyrolysis and carbonization process, the thermal stability of the precursor is improved, and the lignin can more effectively inhibit the rapid concentrated pyrolysis of cellulose, so that the rearrangement of pyrolysis products is weakened. The method is beneficial for preventing overgrowth of hard carbon graphite microcrystals during high-temperature carbonization, so that the hard carbon material with large interlayer spacing and abundant small-size closed pores is prepared. The hard carbon material shows high specific capacity and excellent rate capability when being applied to the negative electrode of the sodium-ion battery. Meanwhile, xylose and furfural generated by decomposition of hemicellulose in a liquid phase can be effectively collected, and full-component utilization of biomass is achieved. The requirements of green production are met, and industrial application is easy to realize.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a lignocellulose biomass-based hard carbon negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of electric vehicles and portable smart devices, there is an urgent need for lower-cost and higher-performance energy storage devices. Lithium ion batteries are currently the most successful commercialized energy storage devices due to their high energy density, long cycle life, and low maintenance cost. However, the global lithium resource reserves are limited and unevenly distributed. This leads to high prices of lithium ion batteries, which are difficult to meet the demand for large-scale energy storage. In contrast, sodium resources are abundant, and sodium ions have similar chemical properties to lithium ions. Therefore, sodium ion batteries can well complement the gap of lithium ion batteries in large-scale energy storage. Among them, the preparation of high-performance and low-cost negative electrode materials is crucial for the commercialization of sodium ion batteries.

[0003] Hard carbon is a non-graphitizable carbon material formed by high-temperature carbonization of a thermosetting precursor, and its structure is composed of highly disordered graphite crystallites and highly twisted amorphous carbon. Compared with graphite, it has a larger interlayer spacing (0.37-0.40 nm), more abundant defects and closed pores, which can provide sufficient storage sites for sodium ions. Therefore, hard carbon shows excellent sodium storage performance, with a high reversible specific capacity of 300-400 mAh g -1 and a long and stable cycle life. With its unique structure and excellent sodium storage performance, hard carbon has become the most commercially valuable negative electrode material for sodium ion batteries. At present, the precursors of hard carbon mainly include pitch-based, resin-based and biomass-based. Among them, the pitch-based carbonization process releases sulfur gas, resulting in high environmental protection cost, low specific capacity of derived hard carbon and low process maturity; the resin-based hard carbon is expensive to prepare, the preparation process is complex, and the carbon yield is low; biomass-based is widely available and environmentally friendly, and is an ideal precursor for preparing high-performance hard carbon.

[0004] Lignocellulosic biomass is a kind of biomass composed of plant cell walls, and its main components are cellulose, hemicellulose and lignin. Lignocellulosic biomass is mainly derived from agricultural waste, forestry waste and energy plants, such as coconut shells, bamboo and straw, etc. They are widely used in the production and research of hard carbon due to their low cost. However, due to the complex structure of lignocellulosic biomass, the three components (cellulose, hemicellulose and lignin) undergo intense and complex interactions during high-temperature pyrolysis and carbonization. Therefore, the hard carbon obtained by direct carbonization of lignocellulosic biomass often has small carbon layer spacing and fewer closed pores, showing low sodium storage capacity and poor rate performance, which cannot meet the requirements of commercialization of sodium-ion batteries. Therefore, it is necessary to pretreat lignocellulosic biomass to regulate its chemical composition and microstructure for the preparation of high-performance lignocellulosic biomass-based derived hard carbon.

[0005] The document (Adv. Mater. 2024, 2412989) reports a method for preparing high-capacity hard carbon by shearing bamboo cells with deep eutectic solvents (DES). After treating the bamboo cells with DES at 120℃ for 6h, most of the amorphous hemicellulose and lignin in the bamboo are successfully removed. The residue obtained by filtering the mixture is dried and then pre-annealed at 400℃ for 2h. Then, the pre-annealed product is immersed in a hydrochloric acid solution and stirred for 4h to remove impurities. Finally, the sample is placed in a 1300℃ carbonization furnace to prepare hard carbon. The hard carbon prepared by this method has a large number of closed pores, providing sufficient sites for sodium ion storage. Therefore, the hard carbon prepared by this method has a high reversible specific capacity of 422mAh g -1 at 0.03C, and still exhibits a reversible specific capacity of 319mAh g -1 at 6C, showing excellent rate performance. However, the method is complex and cumbersome to operate, and the DES shearing of bamboo cells requires the use of expensive levulinic acid reagent, and the long shearing time reduces the equipment turnover rate, increases energy consumption and production cost, making it difficult to meet the requirements of industrial production.

[0006] Chinese patent application CN118993022A discloses a method for preparing a cyan-modified porous hard carbon material. The biomass is immersed in an alkali solution and then directly pre-carbonized at 650℃ in a nitrogen atmosphere to obtain a lignin-based porous pyrolytic carbon with rich internal defects. Finally, the lignin-based porous pyrolytic carbon is mixed with modified mannose by stirring, and the hard carbon material is obtained by carbonization at 1400℃. The modified aldehyde sugar surface coating material helps to close the pores, forming closed pores and providing more sodium storage active sites. Therefore, the hard carbon prepared by this invention exhibits a high reversible specific capacity of 348mAh g -1 at 0.1C. At the same time, it shows excellent rate performance. At 5C, it still has a specific capacity of 258mAh g -1But the preparation process of this method is complex, and it also needs to use sodium hydroxide or potassium hydroxide and other alkaline solution. At the same time, the modification of mannose needs to add reagents such as ammonium chloride and copper acetate, and the reaction is complex and the operation is cumbersome. Therefore, this method has high production cost and is difficult to meet the requirements of green production.

[0007] The above-mentioned methods for preparing high-capacity and high-rate hard carbon materials are difficult to balance low cost, simple production process, environmental friendliness and other industrial production indicators. Therefore, it is very valuable to develop a simple and efficient, low energy consumption, green and environmentally friendly pretreatment method to selectively regulate the composition and structure of lignocellulosic biomass to prepare high-capacity and high-rate hard carbon materials. SUMMARY

[0008] To solve the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a method for preparing high-capacity and high-rate hard carbon materials using low-corrosive organic acid hydrothermal pretreatment of lignocellulosic biomass precursors, while effectively collecting the liquid products (xylose and furfural) to achieve full component utilization of lignocellulosic biomass.

[0009] The present application selects lignocellulosic biomass (coconut shell powder, bamboo powder, straw, etc.) as the hard carbon precursor, and under hydrothermal conditions, the H + attacks the oxygen atom on the glycosidic bond of hemicellulose, protonates it, causes the glycosidic bond to weaken and break, and hemicellulose is decomposed into xylose. Therefore, the proportion of cellulose and lignin in the pretreated biomass precursor increases, and its crystallinity also increases significantly. Therefore, by changing the component ratio of the three elements of lignocellulosic biomass, destroying its dense structure, the pyrolysis and carbonization process can be effectively changed, and the microcrystalline structure and closed pore structure of the derived hard carbon can be regulated. Compared with the hard carbon prepared by directly carbonizing lignocellulosic biomass, the hard carbon prepared by the present application has a larger interlayer spacing, a larger closed pore volume and a suitable closed pore diameter. Therefore, the lignocellulosic biomass-based hard carbon material prepared by the present application exhibits high sodium storage capacity and excellent rate performance. At the same time, this method can effectively collect xylose and furfural produced by the decomposition of hemicellulose in the liquid phase, achieving full component utilization of lignocellulosic biomass.

[0010] Another purpose of the present application is to provide a lignocellulosic biomass-based hard carbon anode material with high capacity and high rate prepared by the above preparation method, and to effectively collect the products xylose and furfural derived from hemicellulose in lignocellulosic biomass.

[0011] Still another purpose of the present application is to provide the application of the above-mentioned lignocellulosic biomass-based hard carbon anode material with high capacity and high rate in sodium ion batteries.

[0012] To achieve the purpose of the present application, the following technical solutions are adopted:

[0013] In a first aspect, the present application provides a method for preparing a lignocellulosic biomass-based hard carbon negative electrode material with high capacity and high rate capability, comprising the following steps:

[0014] (1) mixing lignocellulosic biomass with acid solution, and performing hydrothermal reaction, filtering the obtained hydrothermal material, separating the filter residue to obtain a hard carbon precursor, and collecting xylose and furfural in the filtrate;

[0015] (2) carbonizing the hard carbon precursor in an inert gas atmosphere to obtain a lignocellulosic biomass-based hard carbon negative electrode material.

[0016] Preferably, the lignocellulosic biomass in step (1) comprises at least one of coconut shell powder, bamboo powder, straw, pine powder and corn cob; more preferably, at least one of coconut shell powder, bamboo powder and straw.

[0017] Preferably, the acid solution in step (1) comprises a maleic acid solution; more preferably, a maleic acid solution, a mixture of maleic acid and citric acid, a mixture of maleic acid and sulfuric acid, or a mixture of maleic acid, citric acid and sulfuric acid.

[0018] In the mixture of maleic acid and citric acid, the mixture of maleic acid and sulfuric acid, or the mixture of maleic acid, citric acid and sulfuric acid, the mass concentration of maleic acid is 1-10% (for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.). Any other specific point value within this numerical range can be selected, and it is not convenient to elaborate one by one here.

[0019] Preferably, the concentration of the acid solution in step (1) is 0-15wt.% (for example, 1wt.%, 2wt.%, 3wt.%, 4wt.%, 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.%, 10wt.%, 11wt.%, 12wt.%, 13wt.%, 14wt.%, 15wt.%, etc.), excluding 0wt.%. Any other specific point value within this numerical range can be selected, and it is not convenient to elaborate one by one here.

[0020] Preferably, the mass ratio of lignocellulosic biomass to acid solution in step (1) is 1:10-20 (for example, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, etc.), and further preferably, the mass ratio of lignocellulosic biomass to acid solution is 1:16. Any other specific point value within this numerical range can be selected, and it is not convenient to elaborate one by one here.

[0021] Preferably, the temperature of the hydrothermal reaction in step (1) is 100-200°C (e.g. 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, etc.), and the time of the hydrothermal reaction is 1-5h (e.g. 1h, 2h, 3h, 4h, 5h, etc.); further preferably, the hydrothermal temperature is 170°C, and the time of the hydrothermal reaction is 4h. Any other specific point value within the above numerical range can be selected, and it is not convenient to repeat here.

[0022] Preferably, the inert gas in step (2) is at least one of a noble gas and nitrogen; the noble gas is at least one of argon and helium.

[0023] Preferably, the flow rate of the inert gas in step (2) is 40-80mL / min -1 (e.g. 40mL / min -1 , 45mL / min -1 , 50mL / min -1 , 55mL / min -1 , 60mL / min -1 , 65mL / min -1 , 70mL / min -1 , 75mL / min -1 , 80mL / min -1 , etc.); more preferably, 60mL / min -1 . Any other specific point value within the above numerical range can be selected, and it is not convenient to repeat here.

[0024] Preferably, the temperature of the carbonization in step (2) is 1000-1400°C (e.g. 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, etc.), and the time is 0.5-8h (e.g. 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, etc.); more preferably, the carbonization is 2-6h; most preferably, 1300°C carbonization for 4h. Any other specific point value within the above numerical range can be selected, and it is not convenient to repeat here.

[0025] Preferably, the heating rate of the carbonization in step (2) is 1-10°C / min -1 (e.g. 1°C / min -1 , 2°C / min -1 , 3°C / min -1 , 4°C / min -1 , 5°C / min -1 , 6°C / min-1 7℃min -1 8℃min -1 9℃min -1 10℃min -1 More preferably, 5℃min -1 Any other specific point value within the numerical range can be selected, which is not listed here.

[0026] In a second aspect, the present application provides a high-capacity and high-rate lignocellulose biomass-based hard carbon negative electrode material prepared by the above preparation method.

[0027] In a third aspect, the present application provides application of the above high-capacity and high-rate lignocellulose biomass-based hard carbon negative electrode material in a sodium ion battery.

[0028] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0029] (1) The present application uses natural lignocellulose biomass as a hard carbon precursor, and uses low-corrosive organic acid or a mixture of organic acid and other acid to obtain the hard carbon precursor through simple acid hydrothermal treatment. The preparation method is simple, can avoid corrosion of the equipment, and can effectively collect xylose and furfural produced by hemicellulose decomposition in the liquid phase, so as to realize full utilization of all components of lignocellulose biomass and development of high-value chemical products. This meets the requirements of green production and is easy to realize industrial application.

[0030] (2) The hemicellulose content of the lignocellulose biomass precursor obtained after hydrothermal treatment of the present application is reduced, and the crystallinity of the material is increased. This improves the thermal stability of the precursor, and lignin can more effectively inhibit the rapid concentrated pyrolysis of cellulose, thereby weakening the rearrangement of pyrolysis products. This is beneficial to prevent excessive growth of hard carbon graphite microcrystals during high-temperature carbonization, thereby preparing a hard carbon material with abundant small-size closed pores.

[0031] (3) The hard carbon material prepared by the acid hydrothermal method of the present application has a large interlayer spacing and a large closed pore volume and a small closed pore diameter. The large interlayer spacing provides a faster diffusion channel for sodium ions to reach the active sites, the large closed pore volume can increase the active sites for sodium storage, and the small closed pore diameter can reduce the energy barrier that needs to be overcome for sodium ion filling. Therefore, the hard carbon negative electrode material prepared by the acid hydrothermal method has excellent rate performance, and this hard carbon material is beneficial to commercial production. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Figure is a three-element (cellulose, lignin and hemicellulose) ratio diagram of the hard carbon precursor after acid liquid hydrothermal treatment of Example 1, Comparative Example 1 and Comparative Example 4.

[0033] Figure 2 The graph shows the proportions of xylose and furfural in the filtrate of the hydrothermal materials of Example 1 and Comparative Example 4.

[0034] Figure 3 The images show the XRD patterns of the hard carbon precursors prepared in Example 1 and Comparative Example 1.

[0035] Figure 4 The images show the XRD patterns of the lignocellulosic biomass-based hard carbon materials prepared in Example 1 and Comparative Example 1.

[0036] Figure 5 The image shows the SAXS diagrams of the lignocellulosic biomass-based hard carbon materials prepared in Example 1 and Comparative Example 1.

[0037] Figure 6 The hard carbon materials prepared in Example 1, Comparative Example 1, and Comparative Example 4 were used as anodes in sodium-ion batteries at 0.05 Ag. -1 The second charge-discharge cycle at current density.

[0038] Figure 7 The hard carbon materials prepared in Example 1, Comparative Example 1, and Comparative Example 4 were used as negative electrodes in sodium-ion batteries, and their performance was tested at different current densities (0.05–5 Ag). -1 The rate performance diagram.

[0039] Figure 8 The hard carbon materials prepared in Example 1 and Comparative Example 1 were used as the negative electrodes of sodium-ion batteries at 1Ag. -1 Cyclic performance at current density. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0041] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0042] Example 1

[0043] (1) Mix 2.5g of coconut shell powder with 40g of maleic acid solution with a concentration of 10wt.% and place the mixture in a hydrothermal reactor. Hydrothermal treatment was carried out at 170℃ for 4 hours. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60℃ to obtain the hard carbon precursor CS-MA-10.

[0044] (2) The hard carbon precursor from step (1) was subjected to a nitrogen atmosphere with a gas flow rate of 60 mL / min. -1 Below, at 5℃ min -1(1) 2.5 g of coconut shell powder was mixed with 40 g of a maleic acid solution with a concentration of 5 wt.% and then placed in an autoclave, and hydrothermally treated at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the residue was dried at 60 °C to obtain a hard carbon precursor, CS-MA-5.

[0045] Example 2

[0046] (1) 2.5 g of coconut shell powder was mixed with 40 g of a maleic acid solution with a concentration of 5 wt.% and then placed in an autoclave, and hydrothermally treated at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the residue was dried at 60 °C to obtain a hard carbon precursor, CS-MA-5.

[0047] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at a temperature of 1300 °C under a nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a temperature increase rate of 5 °C min -1 for 4 h to obtain a hard carbon material, which was named CHC-MA-5-1300.

[0048] Example 3

[0049] (1) 2.5 g of coconut shell powder was mixed with 40 g of a maleic acid solution with a concentration of 10 wt.% and then placed in an autoclave, and hydrothermally treated at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the residue was dried at 60 °C to obtain a hard carbon precursor, CS-MA-10.

[0050] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at a temperature of 1000 °C under a nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a temperature increase rate of 5 °C min -1 for 4 h to obtain a hard carbon material, which was named CHC-MA-10-1000.

[0051] Example 4

[0052] (1) 2.5 g of coconut shell powder was mixed with 40 g of a mixed solution of maleic acid and citric acid (the mass concentration of maleic acid was 5%) and then placed in an autoclave, and hydrothermally treated at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the residue was dried at 60 °C to obtain a hard carbon precursor, CS-MCA-10.

[0053] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at a temperature of 1300 °C under a nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a temperature increase rate of 5 °C min -1 for 4 h to obtain a hard carbon material, which was named CHC-MCA-10-1300.

[0054] Example 5

[0055] (1) 2.5 g of coconut shell powder was mixed with 40 g of a mixed solution of maleic acid and sulfuric acid with a concentration of 10 wt.% (mass concentration of maleic acid was 5%) and then placed in an autoclave, and hydrothermally treated at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60 °C to obtain a hard carbon precursor CS-MSA-10.

[0056] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min, with a temperature increase rate of 5 °C / min, to obtain a hard carbon material, which was named CHC-MSA-10-1300. -1 -1 (3) The hard carbon material of step (2) was heat treated at 2800 °C for 2 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min, with a temperature increase rate of 5 °C / min, to obtain a hard carbon material, which was named CHC-MSA-10-2800.

[0057] Example 6

[0058] (1) 2.5 g of coconut shell powder was mixed with 40 g of a mixed solution of maleic acid, citric acid and sulfuric acid with a concentration of 10 wt.% (mass concentration of maleic acid was 5%, mass concentration of citric acid was 2.5%, mass concentration of sulfuric acid was 2.5%) and then placed in an autoclave, and hydrothermally treated at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60 °C to obtain a hard carbon precursor CS-MCSA-10.

[0059] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min, with a temperature increase rate of 5 °C / min, to obtain a hard carbon material, which was named CHC-MCSA-10-1300. -1 -1 (3) The hard carbon material of step (2) was heat treated at 2800 °C for 2 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min, with a temperature increase rate of 5 °C / min, to obtain a hard carbon material, which was named CHC-MCSA-10-2800.

[0060] Example 7

[0061] (1) 2.5 g of bamboo powder was mixed with 40 g of a solution of maleic acid with a concentration of 10 wt.% and then placed in an autoclave, and hydrothermally treated at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60 °C to obtain a hard carbon precursor B-MA-10.

[0062] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min, with a temperature increase rate of 5 °C / min, to obtain a hard carbon material, which was named BHC-MA-10-1300. -1 -1 (3) The hard carbon material of step (2) was heat treated at 2800 °C for 2 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min, with a temperature increase rate of 5 °C / min, to obtain a hard carbon material, which was named BHC-MA-10-2800.

[0063] Example 8

[0064] ​​​(1) 2.5 g of straw powder was mixed with 40 g of a maleic acid solution with a concentration of 10 wt.% and then placed in an autoclave, and hydrothermal treatment was performed at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60 °C to obtain a hard carbon precursor S-MA-10.

[0065] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min with a temperature increase rate of 5 °C / min to obtain a hard carbon material, which was named SHC-MA-10-1300. -1 -1 (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min with a temperature increase rate of 5 °C / min to obtain a hard carbon material, which was named SHC-MA-10-1300.

[0066] Comparative Example 1 (compared with Example 1, no acid liquid hydrothermal treatment)

[0067] (1) 2.5 g of coconut shell powder was mixed with 40 g of a maleic acid solution with a concentration of 10 wt.% and then placed in an autoclave, and hydrothermal treatment was performed at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60 °C to obtain a hard carbon precursor S-MA-10. -1 -1 (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min with a temperature increase rate of 5 °C / min to obtain a hard carbon material, which was named SHC-MA-10-1300.

[0068] Comparative Example 2 (compared with Example 7, no acid liquid hydrothermal treatment)

[0069] (1) 2.5 g of coconut shell powder was mixed with 40 g of a maleic acid solution with a concentration of 10 wt.% and then placed in an autoclave, and hydrothermal treatment was performed at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60 °C to obtain a hard carbon precursor S-MA-10. -1 -1 (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min with a temperature increase rate of 5 °C / min to obtain a hard carbon material, which was named SHC-MA-10-1300.

[0070] Comparative Example 3 (compared with Example 8, no acid liquid hydrothermal treatment)

[0071] (1) 2.5 g of coconut shell powder was mixed with 40 g of a maleic acid solution with a concentration of 10 wt.% and then placed in an autoclave, and hydrothermal treatment was performed at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60 °C to obtain a hard carbon precursor S-MA-10. -1 -1 (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min with a temperature increase rate of 5 °C / min to obtain a hard carbon material, which was named SHC-MA-10-1300.

[0072] Comparative Example 4 (compared with Example 1, hydrothermal treatment with a sulfuric acid solution with the same concentration)

[0073] (1) 2.5 g of coconut shell powder was mixed with 40 g of a maleic acid solution with a concentration of 10 wt.% and then placed in an autoclave, and hydrothermal treatment was performed at 170 °C for 4 h. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60 °C to obtain a hard carbon precursor S-MA-10.

[0074] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized at 1300 °C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL / min with a temperature increase rate of 5 °C / min to obtain a hard carbon material, which was named SHC-MA-10-1300. -1 ​​​​heated at a ramping rate of 5 °C min -1 to 1300 °C for 4 h to obtain a hard carbon material, named as CHC-SA-10-1300.

[0075] Comparative Example 5 (compared with Example 1, hydrothermal treatment with the same concentration of citric acid solution)

[0076] (1) 2.5 g of coconut shell powder was mixed with 40 g of a citric acid solution with a concentration of 10 wt.% and then placed in a hydrothermal kettle for hydrothermal treatment at 170 °C for 4 h. The hydrothermal material was filtered, and the filtrate was collected. The filter residue was dried at 60 °C to obtain a hard carbon precursor, CS-CA-10.

[0077] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized in a nitrogen atmosphere at a gas flow rate of 60 mL min -1 to 1300 °C at a ramping rate of 5 °C min -1 for 4 h to obtain a hard carbon material, named as CHC-CA-10-1300.

[0078] Comparative Example 6 (compared with Example 1, hydrothermal treatment with a high concentration of sulfuric acid solution)

[0079] (1) 2.5 g of coconut shell powder was mixed with 40 g of a sulfuric acid solution with a concentration of 64 wt.% and then placed in a hydrothermal kettle for hydrothermal treatment at 45 °C for 1 h. The hydrothermal material was filtered, and the filtrate was collected. The filter residue was dried at 60 °C to obtain a hard carbon precursor, CS-SA-64.

[0080] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized in a nitrogen atmosphere at a gas flow rate of 60 mL min -1 to 1300 °C at a ramping rate of 5 °C min -1 for 4 h to obtain a hard carbon material, named as CHC-SA-64-1300.

[0081] Comparative Example 7 (compared with Example 1, only immersed in a maleic acid solution without hydrothermal reaction)

[0082] (1) 2.5 g of coconut shell powder was mixed with 40 g of a maleic acid solution with a concentration of 10 wt.% and then immersed for 4 h. The mixed solution was filtered, and the filtrate was collected. The filter residue was dried at 60 °C. The dried filter residue was placed in a muffle furnace at 170 °C for thermal reaction for 4 h to obtain a hard carbon precursor, CS-MA-10-1.

[0083] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized in a nitrogen atmosphere at a gas flow rate of 60 mL min -1 to 1300 °C at a ramping rate of 5 °C min -1The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named CHC-MA-10-1-1300.

[0084] Comparative Example 8 (compared to Example 1, hydrothermal treatment was performed directly in water)

[0085] (1) Mix 2.5g of coconut shell powder with 40g of purified water and place it in a hydrothermal reactor. Hydrothermal treatment was carried out at 170℃ for 4 hours. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60℃ to obtain the hard carbon precursor CS-MA-0.

[0086] (2) The hard carbon precursor from step (1) was subjected to a nitrogen atmosphere at a gas flow rate of 60 mL / min. -1 Below, at 5℃min -1 The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named CHC-MA-0-1300.

[0087] Comparative Example 9 (compared to Example 1, hydrothermal treatment was performed using a 20 wt.% maleic acid solution)

[0088] (1) Mix 2.5g of coconut shell powder with 40g of maleic acid solution with a concentration of 20wt.% and place the mixture in a hydrothermal reactor. Hydrothermal treatment was carried out at 170℃ for 4 hours. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60℃ to obtain the hard carbon precursor CS-MA-20.

[0089] (2) The hard carbon precursor in step (1) was heated to 1300℃ and carbonized for 4h at a heating rate of 5℃min-1 under a nitrogen atmosphere and a gas flow rate of 60mLmin-1 to obtain the hard carbon material, named CHC-MA-20-1300.

[0090] Comparative Example 10 (Carbonized at 1500°C compared to Example 1)

[0091] (1) Mix 2.5g of coconut shell powder with 40g of maleic acid solution with a concentration of 10wt.% and place the mixture in a hydrothermal reactor. Hydrothermal treatment was carried out at 170℃ for 4 hours. The hydrothermal material was filtered, the filtrate was collected, and the filter residue was dried at 60℃ to obtain the hard carbon precursor CS-MA-10.

[0092] (2) The hard carbon precursor from step (1) was subjected to a nitrogen atmosphere at a gas flow rate of 60 mL / min. -1 Below, at 5℃min -1 The temperature was increased to 1500℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named CHC-MA-10-1500.

[0093] The specific preparation method of the negative electrode material and sodium-ion battery includes the following steps:

[0094] The hard carbon material was dried in a 80℃ drying oven for 12h. The hard carbon material: conductive carbon black: sodium polyacrylate were mixed in a mass ratio of 8:1:1, grinded uniformly and coated on the copper foil, and then dried in a 80℃ vacuum drying oven for 12h to obtain the electrode sheet. The battery assembly was carried out in an argon-protected glove box, and the electrolyte was 1mol / L NaPF6 ethylene glycol dimethyl ether solution, and the metal sodium sheet was the counter electrode. -1 NaPF6 ethylene glycol dimethyl ether solution, and the metal sodium sheet was the counter electrode.

[0095] Figure 1 The three-element proportion diagram of the hard carbon precursor after acid hydrothermal treatment of Example 1, Comparative Example 1 and Comparative Example 4 of the present application. As can be seen from the figure, the acid hydrothermal successfully removes the hemicellulose in the biomass, so that the proportion of cellulose and lignin increases, proving that the acid hydrothermal has the function of regulating the components of the biomass.

[0096] Figure 2 The yield diagram of xylose and furfural in the filtrate of the hydrothermal material of Example 1 and Comparative Example 4. The hemicellulose with poor thermal stability in the lignocellulosic biomass is hydrothermally decomposed into xylose and furfural. Compared with sulfuric acid treatment, the maleic acid hydrothermal treatment of coconut shell powder in Example 1 can more effectively collect xylose and furfural to make full use of the hemicellulose in the biomass.

[0097] Figure 3 The XRD diagram of the hard carbon precursor prepared in Example 1 and Comparative Example 1. After maleic acid hydrothermal treatment, the crystallinity of the precursor is greatly improved. This is because the amorphous hemicellulose in the lignocellulosic biomass is effectively removed, and the proportion of cellulose and lignin increases, resulting in an increase in the overall crystallinity of the biomass.

[0098] Figure 4 The XRD diagram of the lignocellulosic biomass-based hard carbon material prepared in Example 1 and Comparative Example 1. Comparing the two hard carbon materials, the hard carbon of Example 1 has a larger interlayer spacing. This facilitates the rapid transmission of sodium ions. This may be because the acid hydrothermal can remove the hemicellulose with low thermal stability, weaken the interaction between lignin and hemicellulose, so that the lignin can better affect the pyrolysis and carbonization process of cellulose, and inhibit the excessive graphitization of cellulose in the high-temperature carbonization process.

[0099] Figure 5 The SAXS diagram of the hard carbon prepared in Example 1 and Comparative Example 1. As shown in the figure, the SAXS curve of the hard carbon of Example 1 has a larger slope than that of Comparative Example 1, indicating that the hard carbon of Example 1 has a larger interlayer spacing. The shoulder of the peak is more obvious, indicating that it has a larger closed pore volume. This is because its smaller graphite crystallites are more conducive to the formation of closed pores, providing more filling sites for sodium ion storage, thereby increasing the platform capacity of the negative electrode. At the same time, through Teubner-Strey model fitting, it is found that the hard carbon prepared in Example 1 has a smaller closed pore aperture (1.64 nm), which is significantly smaller than that of the hard carbon prepared in Comparative Example 1 (2.30 nm). The small aperture of the closed pore effectively reduces the formation energy barrier of sodium clusters, so as to improve the rate performance of the negative electrode.

[0100] Figure 6 The carbon materials prepared in Example 1, Comparative Example 1 and Comparative Example 4 were used as negative electrodes of sodium ion batteries for the second cycle charge-discharge diagram at a current density of 0.05 Ag -1 -1. The hard carbon negative electrode prepared in Example 1 showed a higher specific capacity of 365 mAh g -1 -1. Compared with Comparative Example 1, its specific capacity increased by 105 mAh g -1 -1; compared with Comparative Example 4, its specific capacity increased by 53 mAh g -1 -1. This is because its larger closed pore volume can provide more filling sites for sodium ions.

[0101] Figure 7 The rate performance diagram of the hard carbon prepared in Example 1, Comparative Example 1 and Comparative Example 4 as the negative electrode of the sodium ion battery at different current densities. The hard carbon negative electrode prepared in Example 1 has ultra-high rate performance, which still has a specific capacity of 260 mAh g -1 -1 at a large current density of 5 Ag -1 -1, and the capacity retention rate is 71%. While the hard carbon negative electrode prepared in Comparative Example 1 has a specific capacity of only 53 mAh g -1 -1 at a large current density of 5 Ag -1 -1, and the capacity retention rate is 20%; the hard carbon negative electrode prepared in Comparative Example 4 has a specific capacity of 128 mAh g -1 -1 at a large current density of 5 Ag -1 -1, and the capacity retention rate is 41%. The hard carbon negative electrode prepared in Example 1 has ultra-high rate performance because its larger interlayer spacing provides a faster diffusion channel for sodium ions to reach the active sites, and the smaller closed pore aperture can reduce the energy barrier that needs to be overcome for sodium ion filling.

[0102] Figure 8 The cycle performance diagram of the hard carbon prepared in Example 1 and Comparative Example 1 as the negative electrode of the sodium ion battery at a current density of 1 Ag -1 -1. The hard carbon negative electrode of Example 1 showed excellent cycle stability. After 1500 cycles, its specific capacity was still 293.46 mAh g -1The capacity retention reached 92%. This is due to the large interlayer spacing of the hard carbon negative electrode, which can buffer the volume change of the carbon layer caused by the deintercalation of sodium ions, thereby exhibiting stable sodium storage performance.

[0103] Table 1 is a comparison of the specific capacity, plateau capacity (0.05 Ag -1 ) and rate performance of the hard carbon materials prepared in the above examples and the hard carbon materials prepared in the above comparative examples, wherein the capacity retention ratio is the ratio of the specific capacity at 0.05 Ag -1 to the specific capacity at 0.05 Ag -1 .

[0104] Table 1

[0105]

[0106]

[0107] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are included in the protection scope of the present application.

Claims

1. A method for preparing a lignocellulose biomass-based hard carbon anode material, characterized in that, Includes the following steps: (1) Mix lignocellulose biomass with acid solution and carry out hydrothermal reaction. Filter the resulting hydrothermal material. The filter residue is a hard carbon precursor. Collect xylose and furfural in the filtrate. (2) The hard carbon precursor is carbonized in an inert gas atmosphere to obtain lignocellulose biomass-based hard carbon anode material.

2. The method for preparing a lignocellulosic biomass-based hard carbon anode material according to claim 1, characterized in that, The acid solution in step (1) includes a maleic acid solution; more preferably, a maleic acid solution, a mixture of maleic acid and citric acid, a mixture of maleic acid and sulfuric acid, or a mixture of maleic acid, citric acid and sulfuric acid. In the mixture of maleic acid and citric acid, the mixture of maleic acid and sulfuric acid, or the mixture of maleic acid, citric acid and sulfuric acid, the mass concentration of maleic acid is 1-10%.

3. The method for preparing a lignocellulosic biomass-based hard carbon anode material according to claim 1 or 2, characterized in that, The concentration of the acid solution in step (1) is 0–15 wt.%, excluding 0 wt.%.

4. The method for preparing a lignocellulosic biomass-based hard carbon anode material according to claim 1 or 2, characterized in that, The mass ratio of lignocellulose biomass to acid solution in step (1) is 1:10-20.

5. The method for preparing a lignocellulosic biomass-based hard carbon anode material according to claim 1 or 2, characterized in that, The temperature of the hydrothermal reaction in step (1) is 100-200℃, and the reaction time is 1-5h.

6. The method for preparing a lignocellulosic biomass-based hard carbon anode material according to claim 1 or 2, characterized in that, The carbonization temperature in step (2) is 1000–1400℃, and the time is 0.5–8h; More preferably, carbonization takes 2 to 6 hours.

7. The method for preparing a lignocellulosic biomass-based hard carbon anode material according to claim 1 or 2, characterized in that, The inert gas in step (2) is at least one of a rare gas and nitrogen; the rare gas is at least one of argon and helium. And / or, the flow rate of the inert gas in step (2) is 40–80 mL / min. -1 ; And / or, the heating rate for carbonization in step (2) is 1–10 °C / min. -1 .

8. The method for preparing a lignocellulosic biomass-based hard carbon anode material according to claim 1 or 2, characterized in that, The lignocellulose biomass in step (1) includes at least one of coconut shell powder, bamboo powder, straw, pine powder and corn cob; more preferably, it is at least one of coconut shell powder, bamboo powder and straw.

9. A lignocellulose biomass-based hard carbon anode material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the lignocellulosic biomass-based hard carbon anode material as described in claim 9 in a sodium-ion battery.

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