A high specific capacity, high rate biomass-based hard carbon negative electrode material and a preparation method and application thereof

Abstract

The application discloses a kind of high specific capacity, high rate of biomass-based hard carbon negative material and its preparation method and application.The method is: by hot-pressing method, lignocellulosic biomass is pretreated, then carbonization is carried out under protective gas atmosphere, and hard carbon material is obtained.The hot-pressing method pretreatment process used in the application can make part of hemicellulose decompose, obtain precursor rich in lignin and cellulose, so as to improve the thermal stability of the material.In this process, lignin can effectively inhibit the rapid concentrated pyrolysis of cellulose, and weaken the rearrangement of its pyrolysis products.This not only helps to prevent the excessive growth of hard carbon graphite microcrystal during high-temperature carbonization, but also promotes the generation of small-size closed pore structure, thereby optimizing the microstructure of hard carbon material.The hard carbon material applied to sodium-ion battery negative electrode shows high specific capacity and excellent rate performance.The method has the advantages of simple operation, low equipment requirement, no need to add chemical reagent, green environmental protection and the like.

Description

TECHNICAL FIELD

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

[0002] With the continuous expansion of the scale of renewable energy grid connection, developing low-cost and high-safety large-scale energy storage technology has become the core demand of smart grid construction. Lithium ion batteries have become the most representative electrochemical energy storage technology due to their high energy density, excellent cycle performance and long cycle life. However, the global lithium resource reserves are limited and unevenly distributed, resulting in high cost of lithium ion batteries, which is difficult to meet the economic requirements of large-scale electrochemical energy storage. In contrast, sodium resources show significant advantages due to their abundant reserves, wide distribution and low cost, which makes sodium ion batteries the most promising alternative to lithium ion batteries. However, the performance of the negative electrode material of sodium ion batteries is still the key bottleneck restricting its commercial application.

[0003] Hard carbon material provides sufficient storage sites for sodium ions due to its unique disordered structure of graphite-like microcrystalline, large interlayer spacing (0.37-0.4 nm) and rich nanopore structure. Based on these characteristics, hard carbon has shown advantages such as high reversible capacity (200-400 mAh g -1 ) and long cycle life in sodium storage, and has become one of the most promising negative electrode materials for sodium ion batteries. At present, the precursors of hard carbon material mainly include three types of pitch-based, resin-based and biomass-based. The pitch-based precursor is difficult to obtain high-performance hard carbon negative electrode material due to its high volatile content and high graphitization degree, and its preparation process has not been optimized; the resin-based precursor is difficult to realize large-scale production due to its high cost; in contrast, the biomass precursor has become the most ideal precursor selection for hard carbon material due to its wide source, low cost and environmental friendliness.

[0004] Lignocellulosic biomass is mainly derived from plant tissues. At present, lignocellulosic biomass such as bamboo, straw and coconut shell has been widely used to prepare various carbon materials due to its renewability and low cost. They are potential precursors of hard carbon electrode materials. However, due to the complexity of the composition and structure of lignocellulosic biomass, complex interactions occur during pyrolysis and carbonization, which leads to the difficulty in controlling the structure of hard carbon material prepared by direct carbonization. The interlayer spacing is usually narrow and the closed pore volume is small. This seriously restricts the improvement of specific capacity and rate performance. Therefore, it is necessary to pretreat lignocellulosic biomass and adjust the pyrolysis and carbonization process to prepare hard carbon material with high specific capacity and high rate performance.

[0005] A document (Advanced Energy Materias 2019, 9, 1902852) reported a method to increase the closed pore volume of hard carbon materials by pre-carbonization and high-temperature carbonization. The hard carbon prepared by pre-carbonization at 800℃ and high-temperature carbonization at 1600℃ from a cork has the largest closed pore volume, reaching 0.29cm 3 g -1 . This makes its platform capacity increase significantly from 160mAh g -1 to 231mAh g -1 , and the total capacity also increases significantly from 256mAh g -1 to 358mAh g -1 . However, the high carbonization temperature makes the closed pore diameter too large (4.5nm), which leads to poor rate performance. Its total capacity is only about 100mAh g -1 at a current density of 2000mAg -1 , and the capacity retention rate is about 27.9%.

[0006] Chinese patent application CN117963885A discloses a method for preparing hard carbon materials by pre-oxidation cross-linking and alkali low-temperature etching and its application. The method first immerses biomass in an alkali solution, then without washing, directly performs low-temperature pre-oxidation in an air atmosphere at 150-300℃. This process promotes the material to shrink and cross-link at low temperature, and also etches and pores the biomass. Finally, the precursor powder obtained by pre-oxidation is mixed with pitch, and high-temperature carbonization is performed to obtain hard carbon materials. The hard carbon material prepared by this method has a total capacity of 305mAh g -1 at 0.1C, and still has a total capacity of 260mAh g -1 at 5C, with a capacity retention rate of up to 85%. However, this method has a complex production process and requires the use of sodium hydroxide solution or potassium hydroxide solution, etc. Alkali solution, which has the problems of high production cost and environmental unfriendliness, is not conducive to large-scale industrial production.

[0007] Chinese patent application CN118894521A discloses a method for preparing hard carbon materials by thermal coupling. The method first pre-carbonizes the biomass precursor at 200-400℃, and then uses the coupling effect of the thermal field and the force field in hot-pressing carbonization to prepare hard carbon materials with high tap density. The hard carbon material prepared by this invention has good electrochemical performance, with a total capacity of 331.9mAh g -1 at 0.1C, and still 143.5mAh g -1 at 5C. However, this method requires applying pressure to the pre-carbonized biomass precursor in a vacuum environment and heating for carbonization, which has a complex production process and high requirements for equipment, and is also not conducive to large-scale industrial application.

[0008] The above method for preparing hard carbon materials with high specific capacity and high rate capability is difficult to simultaneously consider low cost, simple production process, environmental friendliness and other industrial production indicators. Therefore, it is very meaningful to seek a simple and efficient, low energy consumption, green and environmentally friendly pretreatment method to selectively regulate the composition and structure of biomass to prepare hard carbon materials with high specific capacity and high rate capability. SUMMARY

[0009] To solve the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a method for preparing hard carbon materials with high specific capacity and high rate capability by pretreating lignocellulosic biomass precursors by hot pressing.

[0010] The present application selects lignocellulosic biomass (such as bamboo powder, pine powder, corn cob powder and coconut shell powder) as the hard carbon precursor, and removes the hemicellulose with low thermal stability by simple hot pressing, so that the combination between components is more compact. In addition, by regulating the complex structure of the three elements (cellulose, lignin and hemicellulose) in lignocellulosic biomass, the interaction between lignin and hemicellulose is significantly weakened, so that lignin can more effectively inhibit the rapid concentrated pyrolysis of cellulose and inhibit the excessive rearrangement of pyrolysis products. The hard carbon prepared by this method has a larger interlayer spacing, smaller crystallite size, larger closed pore volume and smaller closed pore diameter. These structural characteristics endow the prepared lignocellulosic biomass-based hard carbon material with high specific capacity and excellent rate capability.

[0011] Another purpose of the present application is to provide a lignocellulosic biomass-based hard carbon negative material with high specific capacity and high rate capability prepared by the above preparation method.

[0012] Still another purpose of the present application is to provide the application of the above lignocellulosic biomass-based hard carbon negative material with high specific capacity and high rate capability in sodium ion batteries.

[0013] The purpose of the present application is achieved by the following technical solutions:

[0014] A method for preparing a lignocellulosic biomass-based hard carbon negative material with high specific capacity and high rate capability, comprising the following steps:

[0015] (1) hot pressing the biomass material at 100-250℃ and 10-40MPa to obtain a hard carbon precursor;

[0016] (2) carbonizing the hard carbon precursor in an inert gas atmosphere to obtain a lignocellulosic biomass-based hard carbon negative material.

[0017] Preferably, the biomass material in step (1) is at least one of bamboo powder, pine powder, corn cob powder and coconut shell powder; more preferably, at least one of bamboo powder and coconut shell powder.

[0018] Preferably, the hot-pressing treatment in step (1) is performed for 0.5-4h; more preferably, 1-4h.

[0019] Preferably, the hot-pressing in step (1) is performed at a temperature of 100-200℃ and a pressure of 5-15MPa; more preferably, at a temperature of 150℃ and a pressure of 15MPa.

[0020] 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.

[0021] Preferably, the inert gas in step (2) flows at a rate of 40-80mL / min. -1 ; more preferably, 60mL / min. -1

[0022] Preferably, the carbonization in step (2) is performed at a temperature of 1100-1500℃ for 0.5-8h; more preferably, at a temperature of 1100-1300℃ for 2-6h; most preferably, at a temperature of 1300℃ for 4h.

[0023] Preferably, the carbonization in step (2) is performed at a rate of 1-10℃ / min. -1 ; more preferably, 5℃ / min. -1

[0024] The preparation method produces a biomass-based hard carbon negative electrode material with high specific capacity and high rate capability.

[0025] The biomass-based hard carbon negative electrode material with high specific capacity and high rate capability is applied in a sodium-ion battery.

[0026] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0027] (1) The present application uses natural lignocellulosic biomass as a hard carbon precursor, and directly prepares the hard carbon precursor by a hot-pressing method. The method has a simple preparation process, does not need to introduce any chemical additives, and is easy to realize industrial application.

[0028] (2) After hot-pressing, the lignocellulosic biomass precursor has a significantly reduced hemicellulose content, and a significantly increased content of lignin and cellulose, and the components are more closely combined. This structural change significantly improves the thermal stability of the precursor, so that the lignin can effectively inhibit the rapid concentrated pyrolysis of the cellulose, thereby weakening the rearrangement of the pyrolysis products. This property helps to prevent the excessive growth of hard carbon graphite crystallites during high-temperature carbonization, thereby facilitating the formation of a larger interlayer spacing and abundant small-size closed pores in the hard carbon material.

[0029] ​​(3) The hard carbon material prepared by hot pressing in this invention has a large interlayer spacing, a large closed-pore volume, and a small closed-pore diameter. The large interlayer spacing provides a channel for the rapid diffusion of sodium ions, the large closed-pore volume increases the number of active sites for sodium storage, and the small closed-pore diameter lowers the energy barrier that needs to be overcome during sodium ion filling. Therefore, the hard carbon anode material prepared by hot pressing exhibits high specific capacity and excellent rate performance, and has high commercial value. Attached Figure Description

[0030] Figure 1 The diagram shows the proportions of the three elements (cellulose, lignin, and hemicellulose) in the hard carbon precursors after hot pressing pretreatment in Examples 1, 2, 3, 4, and Comparative Example 1.

[0031] Figure 2 The images show the XRD patterns of the lignocellulosic biomass-based hard charcoal materials prepared in Example 1 and Comparative Example 1.

[0032] Figure 3 The image shows the SAXS diagrams of the lignocellulosic biomass-based hard carbon materials prepared in Example 1 and Comparative Example 1.

[0033] Figure 4 The carbon materials prepared in Example 1 and Comparative Example 1 were used as anodes in sodium-ion batteries at 50 mAg. -1 The second charge-discharge cycle at current density.

[0034] Figure 5 The hard carbon prepared in Example 1 and Comparative Example 1 was used as the negative electrode of a sodium-ion battery, and the results were obtained at different current densities (50-1000 mAg). -1 The rate performance diagram.

[0035] Figure 6 The hard carbon prepared in Example 1 was used as the negative electrode of a sodium-ion battery at 1000 mAg. -1 Cyclic performance at current density. Detailed Implementation

[0036] 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.

[0037] 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 products.

[0038] Example 1

[0039] (1) Place 5g of bamboo powder in a hot press and press it at 150℃ for 2 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor B-150-2-15.

[0040] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized under nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a heating rate of 5 °C min -1 to 1300 °C for 4 h to obtain a hard carbon material, which was named as BHC-150-2-15-1300.

[0041] Example 2

[0042] (1) 5 g of bamboo powder was placed in a hot press and hot-pressed at 100 °C for 2 h at a hot-pressing pressure of 15 MPa to obtain a hard carbon precursor B-100-2-15.

[0043] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized under nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a heating rate of 5 °C min -1 to 1300 °C for 4 h to obtain a hard carbon material, which was named as BHC-100-2-15-1300.

[0044] Example 3

[0045] (1) 5 g of bamboo powder was placed in a hot press and hot-pressed at 200 °C for 2 h at a hot-pressing pressure of 15 MPa to obtain a hard carbon precursor B-200-2-15.

[0046] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized under nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a heating rate of 5 °C min -1 to 1300 °C for 4 h to obtain a hard carbon material, which was named as BHC-200-2-15-1300.

[0047] Example 4

[0048] (1) 5 g of bamboo powder was placed in a hot press and hot-pressed at 150 °C for 1 h at a hot-pressing pressure of 15 MPa to obtain a hard carbon precursor B-150-1-15.

[0049] (2) The hard carbon precursor of step (1) was pyrolyzed and carbonized under nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a heating rate of 5 °C min -1 to 1300 °C for 4 h to obtain a hard carbon material, which was named as BHC-150-1-15-1300.

[0050] Example 5

[0051] (1) Place 5g of bamboo powder in a hot press and press at 150℃ for 4 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor B-150-4-15.

[0052] (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 The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named BHC-150-4-15-1300.

[0053] Example 6

[0054] (1) Place 5g of pine powder in a hot press and press it at 150℃ for 2 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor C-150-2-15.

[0055] (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 The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named CHC-150-2-15-1300.

[0056] Example 7

[0057] (1) Place 5g of corn cob in a hot press and press at 150℃ for 2 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor D-150-2-15.

[0058] (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 The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named DHC-150-2-15-1300.

[0059] Example 8

[0060] (1) Place 5g of coconut shell powder in a hot press and press it at 150℃ for 2 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor E-150-2-15.

[0061] (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 The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named EHC-150-2-15-1300.

[0062] Example 9

[0063] (1) Place 5g of bamboo powder in a hot press and press it at 150℃ for 2 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor B-150-2-15.

[0064] (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 The temperature was increased to 1100℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named BHC-150-2-15-1100.

[0065] Example 10

[0066] (1) Place 5g of bamboo powder in a hot press and press it at 150℃ for 2 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor B-150-2-15.

[0067] (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 The temperature was increased to 1500℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named BHC-150-2-15-1500.

[0068] Comparative Example 1

[0069] Take 5g of bamboo powder (without any treatment) and place it in a nitrogen atmosphere at a gas flow rate of 60mL / 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 BHC-1300.

[0070] Comparative Example 2

[0071] (1) Place 5g of bamboo powder in a hot press and press it at 150℃ for 2 hours. The hot pressing pressure is 0MPa to obtain hard carbon precursor B-150-2-0.

[0072] (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 The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named BHC-150-2-0-1300.

[0073] Comparative Example 3

[0074] (1) Place 5g of bamboo powder in a hot press and press it at 150℃ for 2 hours. The hot pressing pressure is 50MPa to obtain hard carbon precursor B-150-2-50.

[0075] (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 The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named BHC-150-2-50-1300.

[0076] Comparative Example 4

[0077] (1) Place 5g of bamboo powder in a hot press and press it at 300℃ for 2 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor B-300-2-15.

[0078] (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 The temperature was increased to 1300℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named BHC-300-2-15-1300.

[0079] Comparative Example 5

[0080] (1) Place 5g of bamboo powder in a nitrogen atmosphere at a gas flow rate of 60mL / min. -1 Below, at 5℃ min -1 The temperature was increased to 600℃ and pyrolyzed for 2 hours to obtain a pre-carbonized precursor.

[0081] (2) The pre-carbonized precursor from step (1) is placed in a hot press and hot-pressed at 150°C for 2 hours at a pressure of 15 MPa to obtain the hard carbon precursor pre-B-150-2-15.

[0082] (3) The hard carbon precursor from step (2) 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 pre-BHC-150-2-15-1300.

[0083] Comparative Example 6

[0084] (1) Place 5g of bamboo powder in a hot press and press it at 150℃ for 2 hours. The hot pressing pressure is 15MPa to obtain hard carbon precursor B-150-2-15.

[0085] (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 The temperature was increased to 1000℃ and pyrolyzed for 4 hours to obtain a hard carbon material, named BHC-150-2-15-1000.

[0086] Comparative Example 7

[0087] (1) 5 g of bamboo powder was placed in a hot press, and pyrolysis carbonization was carried out at 150°C for 2 h under a pressure of 15 MPa to obtain a hard carbon precursor B-150-2-15.

[0088] (2) The hard carbon precursor of step (1) was pyrolysis carbonized at 1600°C for 4 h under a nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a temperature increasing rate of 5°C min -1 to obtain a hard carbon material, which was named BHC-150-2-15-1600.

[0089] Comparative Example 8

[0090] 5 g of pine wood powder (without any classification treatment) was placed in a nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a temperature increasing rate of 5°C min -1 to 1300°C for pyrolysis carbonization for 4 h to obtain a hard carbon material, which was named CHC-1300.

[0091] Comparative Example 9

[0092] 5 g of corn cob (without any classification treatment) was placed in a nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a temperature increasing rate of 5°C min -1 to 1300°C for pyrolysis carbonization for 4 h to obtain a hard carbon material, which was named DHC-1300.

[0093] Comparative Example 10

[0094] 5 g of coconut shell powder (without any classification treatment) was placed in a nitrogen atmosphere at a gas flow rate of 60 mL min -1 at a temperature increasing rate of 5°C min -1 to 1300°C for pyrolysis carbonization for 4 h to obtain a hard carbon material, which was named EHC-1300.

[0095] The specific preparation method of the negative electrode material and the sodium ion battery comprises the following steps:

[0096] The hard carbon material was dried in a 80°C drying box for 12 h. The hard carbon material, conductive carbon black and sodium polyacrylate were mixed in a mass ratio of 8:1:1, and then coated on a copper foil and dried in a 80°C vacuum drying box for 12 h to obtain an electrode sheet. The battery assembly was carried out in an argon glove box, and the electrolyte was a 1 mol L -1 NaPF6 solution in ethylene glycol dimethyl ether, and a piece of metallic sodium was used as the counter electrode.

[0097] Figure 1 This is a graph showing the proportions of the three elements (cellulose, lignin, and hemicellulose) in the hard carbon precursors after hot-pressing pretreatment according to Examples 1, 2, 3, 4, and Comparative Example 1 of this invention. As can be seen from the graph, hot pressing removes some hemicellulose, increasing the proportions of cellulose and lignin, demonstrating that hot pressing has a role in regulating the composition and structure of biomass.

[0098] Figure 2 These are the XRD patterns of the carbon materials prepared in Example 1 and Comparative Example 1. Compared with the carbon materials of Comparative Examples 1 and 2, the hard carbon of Example 1 has a larger interlayer spacing, which facilitates the rapid transport of sodium ions. This may be because hot pressing can remove hemicellulose, which has low thermal stability, making the inter-component connections more compact; it also changes the composite structure of bamboo powder trifoliate, weakens the interaction between lignin and hemicellulose, thereby allowing lignin to better inhibit the pyrolysis and carbonization process of cellulose and suppress its excessive graphitization during high-temperature carbonization.

[0099] Figure 3 This is the SAXS diagram of the hard carbon prepared in Example 1 and Comparative Example 1. Figure 3 As shown, the SAXS curve of the hard carbon in Example 1 is in The more pronounced shoulder peaks indicate a larger closed-pore volume. This is because the smaller graphite crystallites are more conducive to the formation of closed pores. Furthermore, fitting the Teubner-Strey model revealed that the hard carbon prepared in Example 1 has a smaller closed-pore diameter (1.72 nm), significantly smaller than the hard carbon prepared in Comparative Example 1 (2.12 nm).

[0100] Figure 4 The carbon materials prepared in Example 1 and Comparative Example 1 were demonstrated as anodes in sodium-ion batteries at 50 mA g. -1 The second charge-discharge performance at the current density. As can be seen from the figure, the hard carbon anode prepared in Example 1 exhibits a higher specific capacity, reaching 346 mAh g⁻¹. -1 The platform capacity is 234mAh g. -1 Compared to Comparative Example 1, the platform capacity of Example 1 increased by 51 mAh g. -1 The total capacity increased by 72mAh g -1 This significant performance improvement is attributed to the large closed-cell volume of the hard carbon material in Example 1, which provides more filling sites for sodium ions, thus significantly improving its plateau capacity and total capacity.

[0101] Figure 5 The rate performance of the hard carbon materials prepared in Example 1 and Comparative Example 1 as anodes in sodium-ion batteries at different current densities is demonstrated. The hard carbon anode prepared in Example 1 exhibits excellent rate performance at 5000 mAg. -1It can still maintain 215mAh g at high current density -1 The specific capacity of the anode in Example 1 was 62%, with a capacity retention of 62%. In contrast, the specific capacity of the hard carbon anode in Comparative Example 1 was only 53 mAh g⁻¹ at the same current density, with a capacity retention of 19%. The superior rate performance of the hard carbon anode in Example 1 is mainly attributed to its larger interlayer spacing, which provides faster diffusion channels for sodium ions, while the smaller closed-pore size reduces the energy barrier that needs to be overcome during sodium ion filling.

[0102] Figure 6 The hard carbon prepared in Example 1 was used as the negative electrode of a sodium-ion battery at 1000 mAg. -1 Cyclic performance at current density. This hard carbon anode exhibits good cycling stability, retaining 96% of its initial capacity after 1500 cycles. This is attributed to the large interlayer spacing of the hard carbon anode, which buffers the carbon layer volume changes caused by sodium ion insertion / extraction, thus demonstrating stable sodium storage performance.

[0103] Table 1 shows the specific capacity and plateau capacity (50 mAg) of the hard carbon materials prepared in the above embodiments and the hard carbon materials prepared in the above comparative examples. -1 A comparison of performance in terms of capacity retention and rate capability, with a capacity retention rate of 5000 mAg. -1 Lower specific capacity and 50 mA·g -1 The ratio of the following capacities.

[0104] Table 1

[0105]

[0106]

[0107] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a biomass-based hard carbon negative electrode material, characterized in that, The preparation method comprises the following steps: (1) hot-pressing the biomass material at 100-250 ℃ and 10-40 MPa to obtain a hard carbon precursor; (2) carbonizing the hard carbon precursor in an inert gas atmosphere to obtain a biomass-based hard carbon negative electrode material; In step (1), the biomass material is at least one of bamboo powder, pine powder, corn cob powder and coconut shell powder; In step (1), the hot-pressing time is 0.5-4 h; In step (2), the carbonization temperature is 1100-1500 ℃, and the carbonization time is 0.5-8 h.

2. The method for preparing a biomass-based hard carbon anode material according to claim 1, characterized in that, In step (1), the hot-pressing time is 1-4 h; In step (1), the biomass material is at least one of bamboo powder and coconut shell powder.

3. The method for preparing a biomass-based hard carbon anode material according to claim 1, characterized in that, The heating rate of the carbonization in step (2) is 1 to 10 °C min -1 .

4. The method for preparing a biomass-based hard carbon anode material according to claim 3, characterized in that, In step (2), the carbonization temperature is 1100-1300 ℃, and the carbonization time is 2-6 h.

5. The method for preparing a biomass-based hard carbon anode material according to claim 1, characterized in that, In step (1), the hot-pressing temperature is 100-200 ℃, and the hot-pressing pressure is 10-15 MPa.

6. The method for preparing a biomass-based hard carbon anode material according to claim 5, characterized in that, In step (1), the hot-pressing temperature is 150 ℃, and the hot-pressing pressure is 15 MPa.

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

8. A biomass-based hard carbon negative electrode material prepared by the preparation method in any one of claims 1-7.

9. Application of the biomass-based hard carbon negative electrode material in claim 8 to a sodium ion battery.

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