Sodium-ion battery negative electrode material and preparation method thereof

Abstract

The application provides a sodium ion battery negative electrode material and a preparation method thereof. The preparation method of the sodium ion battery negative electrode material comprises the following steps: obtaining a coal-based raw material; performing a defect operation on the coal-based raw material, so that the coal-based raw material is oxidized and crosslinked to obtain a pre-oxidized coal-based negative electrode material; performing a hot extraction treatment on the pre-oxidized coal-based negative electrode material to remove organic impurities in the pre-oxidized coal-based negative electrode material; and performing a high-temperature doping operation on the pre-oxidized coal-based negative electrode material after the hot extraction treatment to obtain the sodium ion battery negative electrode material. The preparation method of the sodium ion battery negative electrode material can effectively change the disorder degree of the microstructure, increase the interlayer spacing of the coal-based raw material, and further effectively improve the reversible specific capacity and the cycle performance.

Description

Technical Field

[0001] This invention relates to the field of electrochemical materials technology, and in particular to a sodium-ion battery anode material and its preparation method. Background Technology

[0002] Sodium is abundant and sodium ions have similar redox potentials and physicochemical properties to lithium ions, making it a potential alternative to lithium-ion batteries as a low-cost energy storage device. However, due to the large radius of sodium ions, it is not easy to find suitable electrode materials to support the reversible and repeated insertion / extraction of large-sized sodium ions. Therefore, exploring sodium-ion battery anode materials with low cost, high reversible specific capacity and stable cycle performance is of great practical significance.

[0003] Currently, coal-based raw materials are suitable as production raw materials for low-cost sodium-ion battery anode materials due to their low price and ease of processing. However, coal-based raw materials are prone to graphitization during carbonization, which makes the carbon layer arrangement of the resulting carbon anode material more ordered, with smaller interlayer spacing and insufficient sodium storage sites. Furthermore, the carbon interlayer spacing is prone to shrinkage or interlayer translation during charge and discharge, resulting in a decrease in the sodium storage capacity of the anode, and the capacity decays rapidly with the increase of cycle number.

[0004] For example, Chinese invention patent applications with application numbers 202310115655.2, 202211040373.2, and 202310490121.8 all involve high-temperature doping of coal-based raw materials. Specifically, this involves increasing the porosity of the coal-based raw materials and allowing the dopant to be incorporated into the pores, thereby improving conductivity and increasing sodium storage space. However, in reality, increasing sodium storage space solely by increasing the porosity of coal-based raw materials is relatively limited. There is still a tendency for the carbon layer arrangement of coal-based raw materials to become more ordered, or for the carbon layer spacing to decrease or for interlayer translation to occur. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a sodium-ion battery anode material and its preparation method that can effectively change the disorder of the microstructure, increase the interlayer spacing of coal-based raw materials, and thus effectively improve the reversible specific capacity and cycle performance.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a sodium-ion battery anode material includes the following steps:

[0008] Obtaining coal-based raw materials;

[0009] The coal-based raw material is subjected to a defect-enhancing process to induce oxidative cross-linking, thereby obtaining a pre-oxidized coal-based anode material.

[0010] The pre-oxidized coal-based anode material is subjected to thermal extraction treatment to remove organic impurities from the pre-oxidized coal-based anode material;

[0011] The pre-oxidized coal-based anode material after thermal extraction was subjected to high-temperature doping to obtain a sodium-ion battery anode material.

[0012] In one embodiment, the coal-based raw material includes at least one of anthracite, bituminous coal, coking coal, and lignite.

[0013] In one embodiment, the coal-based raw material is subjected to a defect-reducing operation, specifically by performing microwave heat treatment on the coal-based raw material under oxygen conditions.

[0014] In one embodiment, the pre-oxidized coal-based anode material is thermally extracted using an organic solvent.

[0015] In one embodiment, the organic solvent is N-methylpyrrolidone.

[0016] In one embodiment, the pre-oxidized coal-based anode material after thermal extraction is subjected to high-temperature doping, including the following steps:

[0017] Obtain the dopant source;

[0018] The doping source and the pre-oxidized coal-based negative electrode material are placed at the inlet and outlet respectively. Inert gas is introduced into the inlet and the inert gas flows to the outlet.

[0019] The doping source and the pre-oxidized coal-based anode material are subjected to heat treatment by heating.

[0020] In one embodiment, the doping source includes at least one of elemental sulfur, elemental phosphorus, tin sulfide, and antimony sulfide.

[0021] In one embodiment, the flow rate of the inert gas is 20 mL / min to 60 mL / min.

[0022] In one embodiment, the doped source and the pre-oxidized coal-based anode material are subjected to a heating treatment, heated to 1000℃~1500℃ at a heating rate of 5℃ / min~8℃ / min, and then held at the temperature for 5h~8h.

[0023] A sodium-ion battery anode material is prepared by the method for preparing sodium-ion battery anode materials described in any of the above embodiments.

[0024] Compared with the prior art, the present invention has at least the following advantages:

[0025] The present invention discloses a method for preparing sodium-ion battery anode materials. This method utilizes coal-based raw materials, effectively reducing the cost of obtaining the anode materials. Further defect-enhancing operations are performed on the coal-based raw materials to increase the number of oxygen-containing groups and vacancy defects, thereby altering the disorder of the microstructure. This makes the coal-based raw materials more susceptible to forming covalent bonds with dopant atoms. Combined with thermal extraction of the pre-oxidized coal-based anode materials, organic impurities are removed, fully exposing the porous structure and facilitating the adsorption of dopant atoms. High-temperature doping of the pre-oxidized coal-based anode materials not only achieves effective and uniform doping within defects and pores but also enables effective molecular-level bonding between dopant atoms and the matrix material. This effectively and stably increases the sodium storage capacity of the anode materials, thereby improving their reversible specific capacity and cycle performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of a method for preparing a sodium-ion battery negative electrode material according to an embodiment of the present invention;

[0028] Figure 2 The graph shows the battery cycle data of coin cells made from the coal-based anode materials obtained in Examples 1 to 5 and the coal-based anode materials obtained in Comparative Examples 1 to 7.

[0029] Figure 3 Here is a SEM image of the coal-based anode material obtained in Example 5;

[0030] Figure 4 This is a TEM image of the coal-based anode material obtained in Example 5;

[0031] Figure 5 The image shows the GCD curve of the coal-based anode material obtained in Example 5. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0033] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] This application provides a method for preparing a sodium-ion battery anode material. The method includes the following steps: obtaining a coal-based raw material; performing a defect-enhancing operation on the coal-based raw material to induce oxidative cross-linking, obtaining a pre-oxidized coal-based anode material; performing a thermal extraction treatment on the pre-oxidized coal-based anode material to remove organic impurities; and performing a high-temperature doping operation on the thermally extracted pre-oxidized coal-based anode material to obtain the sodium-ion battery anode material.

[0036] The aforementioned method for preparing sodium-ion battery anode materials utilizes coal-based raw materials, effectively reducing the cost of obtaining these materials. Further defect-enhancing operations on the coal-based raw materials increase the number of oxygen-containing groups and vacancy defects, altering the disorder of the microstructure and making it easier for the raw materials to form covalent bonds with dopant atoms. Combined with thermal extraction of the pre-oxidized coal-based anode material, organic impurities are removed, fully exposing the porous structure and facilitating the adsorption of dopant atoms. High-temperature doping of the pre-oxidized coal-based anode material not only achieves effective and uniform doping within defects and pores but also enables effective molecular-level bonding between dopant atoms and the matrix material. This effectively and stably increases the sodium storage capacity of the sodium-ion battery anode material, thereby improving its reversible specific capacity and cycle performance.

[0037] To better understand the preparation method of the sodium-ion battery anode material of this application, the following further explanation is provided:

[0038] One embodiment of the method for preparing a sodium-ion battery negative electrode material includes the following steps:

[0039] S100. Obtain coal-based raw materials. It is understandable that coal-based raw materials are relatively inexpensive and easy to process, effectively ensuring a reduction in the cost of obtaining sodium-ion battery anode materials.

[0040] S200. Defecting the coal-based raw material to induce oxidative cross-linking, resulting in a pre-oxidized coal-based anode material. Defecting treatment increases the carbon defects in the coal-based raw material, including at least an increase in oxygen-containing groups and vacancy defects. This alters the disorder of the coal-based raw material's microstructure, making it easier for the raw material to form covalent bonds with dopant atoms. Through doping, not only is the ability of carbon to adsorb sodium at defects activated, but the interlayer spacing of the sodium-ion battery anode material is also increased, which is beneficial for improving the sodium storage space of the sodium-ion battery anode material, thereby increasing its sodium storage capacity.

[0041] S300. The pre-oxidized coal-based anode material is subjected to thermal extraction treatment to remove organic impurities. It can be understood that the removal of organic impurities from the pre-oxidized coal-based anode material is achieved through thermal extraction treatment, i.e., using a solvent to heat and extract the pre-oxidized coal-based anode material. This accelerates the full penetration of the pores of the pre-oxidized coal-based anode material, thereby achieving a more thorough and rapid removal of organic impurities.

[0042] S400. High-temperature doping is performed on the pre-oxidized coal-based anode material after thermal extraction to obtain a sodium-ion battery anode material. It can be understood that by significantly increasing the vacancy defects in the pre-oxidized coal-based anode material and fully exposing its pore structure, high-temperature doping not only achieves effective and uniform intramolecular doping in the sodium-ion battery anode material but also effective and uniform intermolecular doping. This effectively and stably increases the sodium storage space of the sodium-ion battery anode material, thereby improving its sodium storage capacity, reversible specific capacity, and cycle performance.

[0043] The aforementioned method for preparing sodium-ion battery anode materials utilizes coal-based raw materials, effectively reducing the cost of obtaining these materials. Further defect-enhancing operations on the coal-based raw materials increase the number of oxygen-containing groups and vacancy defects, altering the disorder of the microstructure and facilitating covalent bonding between the raw materials and dopant atoms. Combined with thermal extraction of the pre-oxidized coal-based anode material, organic impurities are removed, fully exposing the porous structure and facilitating dopant atom adsorption. High-temperature doping of the pre-oxidized coal-based anode material not only achieves effective and uniform doping within defects and pores but also enables effective molecular-level bonding between dopant atoms and the matrix material. This effectively and stably increases the sodium storage capacity of the anode material, thereby improving its reversible specific capacity and cycle performance.

[0044] In one embodiment, the coal-based raw material undergoes a defect-reduction process, specifically by microwave heat treatment under oxygen conditions. It is understood that microwave heat treatment of the coal-based raw material under oxidizing conditions effectively ensures the formation of vacancy defects. Furthermore, due to the high efficiency of microwave heat treatment, the oxidative cross-linking time of the coal-based raw material can be shortened, and the uniformity of vacancy defect formation is achieved. This ensures both the conductivity of the sodium-ion battery anode material and an effective increase in its sodium storage capacity.

[0045] It should be noted that the microwave heating in this application does not utilize its ability to penetrate matter and eliminate "cold centers" to accelerate the breaking of molecular bonds in coal-based raw materials, thereby promoting the formation of gas molecules that overflow from the surface of the coal-based raw materials and increasing the microporous structure of the coal-based raw materials, thus enhancing the uniformity and high doping content of the coal-based raw materials. In reality, a large part of the coal-based raw materials are still just stacked carbon layers, which makes the sodium-ion battery anode materials made from coal-based raw materials still prone to the reduction of carbon interlayer spacing or interlayer translation during charging and discharging. Therefore, in this application, microwave heating is used to pre-treat the coal-based raw materials, that is, to preferentially treat the defects in the coal-based raw materials. Since coal-based materials are thermosensitive materials... Furthermore, the presence of carbon in various structural forms in coal-based raw materials results in uneven heating at every moment during microwave heating, leading to numerous defects within the raw materials. This increase in defects, particularly vacancy defects, causes negative charges to accumulate at sp2 carbon sites near these defects, facilitating covalent bonding with dopant atoms. This doping not only activates the ability of carbon to adsorb sodium at defects but also increases the interlayer spacing of sodium-ion battery anode materials, thereby enhancing the sodium storage capacity of the anode materials.

[0046] In one embodiment, microwave heat treatment of coal-based raw materials at a microwave power of 200W to 1600W effectively ensures the reduction of defects in the coal-based raw materials.

[0047] It should also be noted that simply performing defect treatment on coal-based raw materials under certain microwave heating power conditions has a limited effect on increasing the number of defects in the coal-based raw materials. That is, it cannot ensure an effective increase in the number of defects in the coal-based raw materials to a large extent, thus limiting the improvement of the sodium storage capacity of the sodium-ion battery anode material. Therefore, in this application, in order to better improve the sodium storage capacity of the sodium-ion battery anode material, in one embodiment, the coal-based raw materials are subjected to microwave heat treatment. Specifically, the coal-based raw materials are placed in a microwave oven and subjected to microwave heat treatment at a microwave power of 180W to 220W. The coal-based raw material is subjected to microwave heat treatment for 8 min to 1.2 min, then microwave heat treatment for 0.8 min to 1.2 min at a microwave power of 350 W to 420 W, then microwave heat treatment for 0.8 min to 1.2 min at a microwave power of 580 W to 650 W, then microwave heat treatment for 1.6 min to 2.0 min at a microwave power of 950 W to 1200 W, and finally microwave heat treatment for 4.8 min to 5.5 min at a microwave power of 1500 W to 1800 W.

[0048] It is understandable that this prompts the coal-based raw materials to undergo microwave staged heating, that is, to use microwaves of different powers to sequentially treat the coal-based raw materials for a certain period of time to eliminate defects.

[0049] First, microwave heat treatment of coal-based raw materials with a power of 180W to 220W, which effectively ensures the initial uneven heating of localized coal-based raw materials, for 0.8 to 1.2 minutes, achieves a good initial increase in vacancy defects. However, if the same power microwave is used to further treat the coal-based raw materials, it is difficult to increase the number of vacancy defects effectively; instead, it will only promote the oxidation of the coal-based raw materials, thereby reducing their conductivity. In addition, too short a treatment time will affect the effective increase of vacancy defects in the coal-based raw materials.

[0050] Secondly, microwave heat treatment of coal-based raw materials with a power of 350W to 420W for 0.8 to 1.2 minutes, which effectively ensures the initial localized uneven heating of the coal-based raw materials, achieves a better increase in vacancy defects. However, if the same power microwave is used to treat the coal-based raw materials, it is difficult to increase the number of vacancy defects effectively; it will only accelerate the oxidation of the coal-based raw materials, further reducing their conductivity. Alternatively, using microwaves with larger power variations not only wastes energy but also reduces the increase in the number of vacancy defects formed within the same power range, affecting the defect reduction effect. Similarly, using microwaves with smaller power variations is also difficult to increase the number of vacancy defects effectively; it will only accelerate the oxidation of the coal-based raw materials, further reducing their conductivity. In addition, too short a treatment time will affect the effective increase of vacancy defects in the coal-based raw materials.

[0051] Then, microwave heat treatment of the coal-based raw materials for 0.8 to 1.2 minutes with microwaves of 580 W to 650 W, which have a relatively large power and can effectively ensure the initial local uneven heating of the coal-based raw materials, effectively increased the number of vacancy defects. However, if the same power microwave is used to treat the coal-based raw materials, it is also difficult to effectively increase the number of vacancy defects; it will only promote the oxidation of the coal-based raw materials, which will further reduce the conductivity of the coal-based raw materials. Alternatively, if microwaves with a larger power variation are used to treat the coal-based raw materials, it will not only waste energy but also reduce the increase in the number of vacancy defects formed within the same power range, affecting the defect treatment effect of the coal-based raw materials. Similarly, if microwaves with a small power variation are used to treat the coal-based raw materials, it is also difficult to effectively increase the number of vacancy defects; it will only promote the oxidation of the coal-based raw materials, which will further reduce the conductivity of the coal-based raw materials. In addition, if the treatment time is too short, it will affect the effective increase of vacancy defects in the coal-based raw materials.

[0052] Then, microwave heat treatment of the coal-based raw materials for 1.6 to 2.0 minutes with microwaves of 950 W to 1200 W, which have a larger power range and can effectively ensure the initial localized uneven heating of the coal-based raw materials, effectively increased the number of vacancy defects. However, if the same power microwave is used to treat the coal-based raw materials, it is difficult to increase the number of vacancy defects effectively; it will only accelerate the oxidation of the coal-based raw materials, further reducing their conductivity. Alternatively, using microwaves with larger power variations not only wastes energy but also reduces the increase in the number of vacancy defects formed within the same power range, affecting the defect treatment effect. Similarly, using microwaves with smaller power variations is also difficult to increase the number of vacancy defects effectively; it will only accelerate the oxidation of the coal-based raw materials, further reducing their conductivity. In addition, too short a treatment time will affect the effective increase of vacancy defects in the coal-based raw materials.

[0053] Finally, microwave heat treatment of coal-based raw materials with a power of 1500W to 1800W for 4.8 to 5.5 minutes, which effectively ensures the initial localized uneven heating of the coal-based raw materials, achieved a better increase in the number of vacancy defects. However, if the same power microwave is used to treat the coal-based raw materials, it is difficult to increase the number of vacancy defects effectively; it will only accelerate the oxidation of the coal-based raw materials, further reducing their conductivity. Alternatively, using microwaves with greater power variations not only wastes energy but also reduces the increase in the number of vacancy defects formed within the same power range, affecting the defect reduction effect. Similarly, using microwaves with smaller power variations is also difficult to increase the number of vacancy defects effectively; it will only accelerate the oxidation of the coal-based raw materials, further reducing their conductivity. In addition, too short a treatment time will affect the effective increase in the number of vacancy defects in the coal-based raw materials.

[0054] In one embodiment, the coal-based raw material includes at least one of anthracite, bituminous coal, coking coal, and lignite, which effectively ensures the reduction of the acquisition cost of sodium-ion battery anode material and effectively increases the vacancy defects in the coal-based raw material under microwave treatment.

[0055] In one embodiment, the coal-based raw material includes anthracite, coking coal, and lignite. Further, the mass ratio of anthracite, coking coal, and lignite is 1:(0.2–0.5):(0.1–0.2). It is understood that including anthracite, coking coal, and lignite in a mass ratio of 1:(0.2–0.5):(0.1–0.2) in the coal-based material increases the amount of carbon with different structural forms present in the coal-based material. Furthermore, the microwave treatment exacerbates the uneven heating of the coal-based raw material, making it easier for the coal-based raw material to form covalent bonds with dopant atoms. Thus, the doping of these dopant atoms helps to increase the sodium storage space of the sodium-ion battery anode material, thereby improving the sodium storage capacity of the sodium-ion battery anode material.

[0056] In one embodiment, the oxygen condition is to maintain the oxygen content in the microwave oven at 21% ± 0.5%, which better ensures an increase in the number of vacancy defects formed in the coal-based raw materials during laser heat treatment.

[0057] In one embodiment, the pre-oxidized coal-based anode material is thermally extracted using an organic solvent.

[0058] In one embodiment, the organic solvent is N-methylpyrrolidone, which effectively ensures the full wetting and dissolution of organic impurities in the pores of the pre-oxidized coal-based anode material, thereby effectively ensuring the removal of organic impurities.

[0059] In one embodiment, the pre-oxidized coal-based anode material is thermally extracted using an organic solvent. Specifically, N-methylpyrrolidone is placed in a polytetrafluoroethylene liner and then placed in a hydrothermal reactor. The mixture is heated at 120°C to 150°C for 4 to 6 hours, which effectively ensures the removal of organic impurities.

[0060] In one embodiment, before the step of performing high-temperature doping on the pre-oxidized coal-based anode material after thermal extraction, and after the step of performing thermal extraction on the pre-oxidized coal-based anode material, the method for preparing the sodium-ion battery anode material further includes the following steps:

[0061] Cooling treatment is applied to the pre-oxidized coal-based anode material after thermal extraction.

[0062] The pre-oxidized coal-based anode material after cooling is subjected to filtration treatment;

[0063] The pre-oxidized coal-based anode material after filtration is washed.

[0064] The pre-oxidized coal-based anode material after washing is dried.

[0065] The pre-oxidized coal-based anode material after drying is ground.

[0066] In one embodiment, the pre-oxidized coal-based anode material after thermal extraction is cooled to room temperature.

[0067] In one embodiment, the pre-oxidized coal-based anode material after thermal extraction is subjected to vacuum filtration. Specifically, the pre-oxidized coal-based anode material is placed in an ultrasonic machine for ultrasonic treatment, followed by vacuum filtration through a Buchner funnel. Further, the ultrasonic treatment time is 2 to 3 hours.

[0068] In one embodiment, the pre-oxidized coal-based anode material after thermal extraction is washed with anhydrous ethanol. Further, the washing is performed at least three times. Further, the washing is performed three to five times.

[0069] In one embodiment, the pre-oxidized coal-based anode material after washing is dried at a temperature of 80°C to 90°C. Further, the drying time is 3 to 5 hours. Further, the pre-oxidized coal-based anode material is placed in a drying oven for further drying.

[0070] In one embodiment, the pre-oxidized coal-based anode material after drying is ground, specifically by grinding the pre-oxidized coal-based anode material and passing it through a 200-mesh sieve.

[0071] In one embodiment, the pre-oxidized coal-based anode material after thermal extraction is subjected to high-temperature doping, including the following steps:

[0072] Obtain the dopant source;

[0073] The doping source and the pre-oxidized coal-based anode material are placed at the inlet and outlet respectively. Inert gas is introduced into the inlet and directed to the outlet.

[0074] The doping source and the pre-oxidized coal-based anode material were subjected to heat treatment by heating.

[0075] In one embodiment, the doping source and the pre-oxidized coal-based anode material are placed at the inlet and outlet of a high-temperature tubular furnace, respectively.

[0076] In one embodiment, the doping source includes at least one of elemental sulfur, elemental phosphorus, tin sulfide, and antimony sulfide.

[0077] In one embodiment, the inert gas flow rate is 100 mL / min to 200 mL / min.

[0078] In one embodiment, the doped source and the pre-oxidized coal-based anode material are subjected to a heating heat treatment, heated to 1000℃~1500℃ at a heating rate of 5℃ / min~8℃ / min, and then held at that temperature for 5h~8h.

[0079] In one embodiment, before the step of obtaining the sodium-ion battery anode material and after the step of performing high-temperature doping on the pre-oxidized coal-based anode material after thermal extraction, the method for preparing the sodium-ion battery anode material further includes the following steps:

[0080] The pre-oxidized coal-based anode material is cooled and placed.

[0081] The pre-oxidized coal-based anode material after cooling and placement is ground and sieved.

[0082] In one embodiment, the pre-oxidized coal-based anode material is subjected to a cooling treatment to cool to room temperature.

[0083] In one embodiment, the pre-oxidized coal-based anode material after cooling and placement is ground and sieved, specifically: the pre-oxidized coal-based anode material is ground and then passed through a 200-mesh sieve.

[0084] This application also provides a sodium-ion battery anode material, which is prepared by the preparation method of sodium-ion battery anode material of any of the above embodiments.

[0085] Compared with the prior art, the present invention has at least the following advantages:

[0086] The present invention discloses a method for preparing sodium-ion battery anode materials. This method utilizes coal-based raw materials, effectively reducing the cost of obtaining the anode materials. Further defect-enhancing operations are performed on the coal-based raw materials to increase the number of oxygen-containing groups and vacancy defects, thereby altering the disorder of the microstructure. This makes the coal-based raw materials more susceptible to forming covalent bonds with dopant atoms. Combined with thermal extraction of the pre-oxidized coal-based anode materials, organic impurities are removed, fully exposing the porous structure and facilitating the adsorption of dopant atoms. High-temperature doping of the pre-oxidized coal-based anode materials not only achieves effective and uniform doping within defects and pores but also enables effective molecular-level bonding between dopant atoms and the matrix material. This effectively and stably increases the sodium storage capacity of the anode materials, thereby improving their reversible specific capacity and cycle performance.

[0087] The following are some specific examples. Where %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively cover all possible scenarios, and unless otherwise specified, the materials used in the following examples are commercially available.

[0088] Example 1

[0089] Obtain 2 kg of anthracite;

[0090] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 180W for 1.2 minutes, 350W for 1.2 minutes, 580W for 1.2 minutes, 950W for 2.0 minutes, and 1500W for 5.5 minutes. Then remove the anthracite for later use.

[0091] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of N-methylpyrrolidone was added to the inner liner. Then the inner liner was placed in a hydrothermal reactor and heated at 120℃ for 6 hours. After that, the anthracite was poured out into a beaker and cooled to room temperature.

[0092] The beaker was transferred to an ultrasonic machine and sonicated for 3 hours. Then it was filtered through a Buchner funnel, washed three times with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 5 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0093] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced and the gas flow rate was controlled at 60 mL / min. The temperature was raised to 1000℃ and the heating rate was controlled at 5℃ / min. The temperature was kept constant for 8 hours. Then, the furnace was cooled to room temperature. The material was then removed, ground, and pulverized, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0094] Example 2

[0095] Obtain 2 kg of anthracite;

[0096] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 200W for 1.0min, 390W for 1.0min, 600W for 1.0min, 1100W for 1.8min, and 1650W for 5.0min. Then remove the anthracite for later use.

[0097] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of N-methylpyrrolidone was added to the inner liner. Then the inner liner was placed in a hydrothermal reactor and heated at 135℃ for 5 hours. After that, the anthracite was poured out into a beaker and cooled to room temperature.

[0098] The beaker was transferred to an ultrasonic machine and sonicated for 2.5 hours. Then it was filtered through a Buchner funnel, washed four times with anhydrous ethanol and deionized water, and dried in an oven at 85°C for 4 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0099] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 40 mL / min. The temperature was raised to 1200℃ at a rate of 6℃ / min and held at that temperature for 6.5 h. The furnace was then cooled to room temperature. The material was then removed, ground, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0100] Example 3

[0101] Obtain 2 kg of anthracite;

[0102] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 220W for 0.8 minutes, 420W for 0.8 minutes, 650W for 0.8 minutes, 1200W for 1.6 minutes, and 1800W for 4.8 minutes. Then remove the anthracite for later use.

[0103] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of N-methylpyrrolidone was added to the inner liner. Then the inner liner was placed in a hydrothermal reactor and heated at 150°C for 4 hours. After that, the anthracite was poured out into a beaker and cooled to room temperature.

[0104] The beaker was transferred to an ultrasonic machine and sonicated for 2 hours. Then it was filtered through a Buchner funnel, washed 5 times with anhydrous ethanol and deionized water, and dried in an oven at 90°C for 3 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0105] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 20 mL / min. The temperature was raised to 1500℃ at a rate of 8℃ / min and held at that temperature for 5 hours. The furnace was then cooled to room temperature. The material was then removed, ground, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0106] Example 4

[0107] Obtain a total of 2 kg of anthracite, coking coal and lignite (mass ratio of 1:0.2:0.1);

[0108] Anthracite, coking coal, and lignite were piled in the center of a microwave oven, maintaining an oxygen content of 21%. The mixture was then processed sequentially at microwave power of 180W-220W for 0.8-1.2 minutes, 350W-420W for 0.8-1.2 minutes, 580W-650W for 0.8-1.2 minutes, 950W-1200W for 1.6-2.0 minutes, and 1500W-1800W for 4.8-5.5 minutes. The mixture was then removed and set aside for later use.

[0109] The mixture of anthracite, coking coal and lignite was placed in a 10L polytetrafluoroethylene liner, and 5kg of N-methylpyrrolidone was added to the liner. The liner was then placed in a hydrothermal reactor and heated at 120℃~150℃ for 4h~6h. The mixture of anthracite, coking coal and lignite was then poured into a beaker and cooled to room temperature.

[0110] Transfer the beaker to an ultrasonic machine and sonicate for 2-3 hours. Then filter it through a Buchner funnel, wash it repeatedly with anhydrous ethanol and deionized water 3-5 times, and then dry it in an oven at 80-90°C for 3-5 hours. Remove it, grind it, and pass it through a 200-mesh sieve to obtain a purified mixture of anthracite, coking coal and lignite.

[0111] The purified mixture of anthracite, coking coal, and lignite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 20-60 mL / min, and the temperature was raised to 1000-1500℃ at a rate of 5-8℃ / min. The temperature was maintained for 5-8 hours, and then the mixture was cooled to room temperature with the furnace. The mixture was then removed, ground, and pulverized, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0112] Example 5

[0113] Obtain a total of 2 kg of anthracite, coking coal and lignite (mass ratio of 1:0.35:0.15);

[0114] Anthracite, coking coal, and lignite were piled in the center of a microwave oven, maintaining an oxygen content of 21%. The mixture was then processed sequentially at microwave power of 180W-220W for 0.8-1.2 minutes, 350W-420W for 0.8-1.2 minutes, 580W-650W for 0.8-1.2 minutes, 950W-1200W for 1.6-2.0 minutes, and 1500W-1800W for 4.8-5.5 minutes. The mixture was then removed and set aside for later use.

[0115] The mixture of anthracite, coking coal and lignite was placed in a 10L polytetrafluoroethylene liner, and 5kg of N-methylpyrrolidone was added to the liner. The liner was then placed in a hydrothermal reactor and heated at 120℃~150℃ for 4h~6h. The mixture of anthracite, coking coal and lignite was then poured into a beaker and cooled to room temperature.

[0116] Transfer the beaker to an ultrasonic machine and sonicate for 2-3 hours. Then filter it through a Buchner funnel, wash it repeatedly with anhydrous ethanol and deionized water 3-5 times, and then dry it in an oven at 80-90°C for 3-5 hours. Remove it, grind it, and pass it through a 200-mesh sieve to obtain a purified mixture of anthracite, coking coal and lignite.

[0117] The purified mixture of anthracite, coking coal, and lignite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 20-60 mL / min, and the temperature was raised to 1000-1500℃ at a rate of 5-8℃ / min. The temperature was maintained for 5-8 hours, and then the mixture was cooled to room temperature with the furnace. The mixture was then removed, ground, and pulverized, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0118] Example 6

[0119] Obtain a total of 2 kg of anthracite, coking coal and lignite (mass ratio of 1:0.5:0.2);

[0120] Anthracite, coking coal, and lignite were piled in the center of a microwave oven, maintaining an oxygen content of 21%. The mixture was then processed sequentially at microwave power of 180W-220W for 0.8-1.2 minutes, 350W-420W for 0.8-1.2 minutes, 580W-650W for 0.8-1.2 minutes, 950W-1200W for 1.6-2.0 minutes, and 1500W-1800W for 4.8-5.5 minutes. The mixture was then removed and set aside for later use.

[0121] The mixture of anthracite, coking coal and lignite was placed in a 10L polytetrafluoroethylene liner, and 5kg of N-methylpyrrolidone was added to the liner. The liner was then placed in a hydrothermal reactor and heated at 120℃~150℃ for 4h~6h. The mixture of anthracite, coking coal and lignite was then poured into a beaker and cooled to room temperature.

[0122] Transfer the beaker to an ultrasonic machine and sonicate for 2-3 hours. Then filter it through a Buchner funnel, wash it repeatedly with anhydrous ethanol and deionized water 3-5 times, and then dry it in an oven at 80-90°C for 3-5 hours. Remove it, grind it, and pass it through a 200-mesh sieve to obtain a purified mixture of anthracite, coking coal and lignite.

[0123] The purified mixture of anthracite, coking coal, and lignite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 20-60 mL / min, and the temperature was raised to 1000-1500℃ at a rate of 5-8℃ / min. The temperature was maintained for 5-8 hours, and then the mixture was cooled to room temperature with the furnace. The mixture was then removed, ground, and pulverized, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0124] Comparative Example 1

[0125] Obtain 2 kg of anthracite;

[0126] Place the anthracite in the center of the microwave oven, maintain the oxygen content in the microwave oven at 21%, process it at a microwave power of 1400w for 9.8 minutes, and then remove the anthracite for later use.

[0127] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of N-methylpyrrolidone was added to the inner liner. Then the inner liner was placed in a hydrothermal reactor and heated at 120℃ for 6 hours. After that, the anthracite was poured out into a beaker and cooled to room temperature.

[0128] The beaker was transferred to an ultrasonic machine and sonicated for 3 hours. Then it was filtered through a Buchner funnel, washed three times with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 5 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0129] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced and the gas flow rate was controlled at 60 mL / min. The temperature was raised to 1000℃ and the heating rate was controlled at 5℃ / min. The temperature was kept constant for 8 hours. Then, the furnace was cooled to room temperature. The material was then removed, ground, and pulverized, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0130] Comparative Example 2

[0131] Obtain 2 kg of anthracite;

[0132] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 170W for 1.2 minutes, 340W for 1.2 minutes, 570W for 1.2 minutes, 940W for 2.0 minutes, and 1400W for 5.5 minutes. Then remove the anthracite for later use.

[0133] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of N-methylpyrrolidone was added to the inner liner. Then the inner liner was placed in a hydrothermal reactor and heated at 120℃ for 6 hours. After that, the anthracite was poured out into a beaker and cooled to room temperature.

[0134] The beaker was transferred to an ultrasonic machine and sonicated for 3 hours. Then it was filtered through a Buchner funnel, washed three times with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 5 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0135] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced and the gas flow rate was controlled at 60 mL / min. The temperature was raised to 1000℃ and the heating rate was controlled at 5℃ / min. The temperature was kept constant for 8 hours. Then, the furnace was cooled to room temperature. The material was then removed, ground, and pulverized, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0136] Comparative Example 3

[0137] Obtain 2 kg of anthracite;

[0138] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 170W for 1.5 minutes, 340W for 1.5 minutes, 570W for 1.5 minutes, 940W for 2.5 minutes, and 1400W for 6.0 minutes. Then remove the anthracite for later use.

[0139] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of N-methylpyrrolidone was added to the inner liner. Then the inner liner was placed in a hydrothermal reactor and heated at 120℃ for 6 hours. After that, the anthracite was poured out into a beaker and cooled to room temperature.

[0140] The beaker was transferred to an ultrasonic machine and sonicated for 3 hours. Then it was filtered through a Buchner funnel, washed three times with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 5 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0141] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced and the gas flow rate was controlled at 60 mL / min. The temperature was raised to 1000℃ and the heating rate was controlled at 5℃ / min. The temperature was kept constant for 8 hours. Then, the furnace was cooled to room temperature. The material was then removed, ground, and pulverized, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0142] Comparative Example 4

[0143] Obtain 2 kg of anthracite;

[0144] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 230W for 0.8 minutes, 430W for 0.8 minutes, 660W for 0.8 minutes, 1250W for 1.6 minutes, and 1850W for 4.8 minutes. Then remove the anthracite for later use.

[0145] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of N-methylpyrrolidone was added to the inner liner. Then the inner liner was placed in a hydrothermal reactor and heated at 150°C for 4 hours. After that, the anthracite was poured out into a beaker and cooled to room temperature.

[0146] The beaker was transferred to an ultrasonic machine and sonicated for 2 hours. Then it was filtered through a Buchner funnel, washed 5 times with anhydrous ethanol and deionized water, and dried in an oven at 90°C for 3 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0147] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 20 mL / min. The temperature was raised to 1500℃ at a rate of 8℃ / min and held at that temperature for 5 hours. The furnace was then cooled to room temperature. The material was then removed, ground, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0148] Comparative Example 5

[0149] Obtain 2 kg of anthracite;

[0150] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 230W for 1.0min, 430W for 1.0min, 660W for 1.0min, 1250W for 2.0min, and 1850W for 5.0min. Then remove the anthracite for later use.

[0151] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of N-methylpyrrolidone was added to the inner liner. Then the inner liner was placed in a hydrothermal reactor and heated at 150°C for 4 hours. After that, the anthracite was poured out into a beaker and cooled to room temperature.

[0152] The beaker was transferred to an ultrasonic machine and sonicated for 2 hours. Then it was filtered through a Buchner funnel, washed 5 times with anhydrous ethanol and deionized water, and dried in an oven at 90°C for 3 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0153] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 20 mL / min. The temperature was raised to 1500℃ at a rate of 8℃ / min and held at that temperature for 5 hours. The furnace was then cooled to room temperature. The material was then removed, ground, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0154] Comparative Example 6

[0155] Obtain 2 kg of anthracite;

[0156] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 200W for 1.0min, 390W for 1.0min, 600W for 1.0min, 1100W for 1.8min, and 1650W for 5.0min. Then remove the anthracite to a beaker and cool it to room temperature.

[0157] The beaker was transferred to an ultrasonic machine and sonicated for 2.5 hours. Then it was filtered through a Buchner funnel, washed four times with anhydrous ethanol and deionized water, and dried in an oven at 85°C for 4 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0158] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 40 mL / min. The temperature was raised to 1200℃ at a rate of 6℃ / min and held at that temperature for 6.5 h. The furnace was then cooled to room temperature. The material was then removed, ground, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0159] Comparative Example 7

[0160] Obtain 2 kg of anthracite;

[0161] Place the anthracite in the center of the microwave oven, maintaining an oxygen content of 21%. Sequentially adjust the microwave power to 200W for 1.0min, 390W for 1.0min, 600W for 1.0min, 1100W for 1.8min, and 1650W for 5.0min. Then remove the anthracite for later use.

[0162] The removed anthracite was placed in a 10L polytetrafluoroethylene inner liner, and 5kg of a 1:1 mixture of concentrated sulfuric acid and concentrated nitric acid was added to the inner liner. The inner liner was then placed in a hydrothermal reactor and heated at 135℃ for 5 hours. The anthracite was then poured out into a beaker and cooled to room temperature.

[0163] The beaker was transferred to an ultrasonic machine and sonicated for 2.5 hours. Then it was filtered through a Buchner funnel, washed four times with anhydrous ethanol and deionized water, and dried in an oven at 85°C for 4 hours. The beaker was then ground and passed through a 200-mesh sieve to obtain purified anthracite.

[0164] The purified anthracite was placed at the outlet of a high-temperature tubular furnace, and antimony sulfide was placed at the inlet of the furnace. Inert gas was introduced at a flow rate of 40 mL / min. The temperature was raised to 1200℃ at a rate of 6℃ / min and held at that temperature for 6.5 h. The furnace was then cooled to room temperature. The material was then removed, ground, and passed through a 200-mesh sieve to obtain the coal-based anode material.

[0165] The coal-based anode materials obtained in Examples 1 to 5 and the coal-based anode materials obtained in Comparative Examples 1 to 7 were used as counter electrodes to prepare coin cell half-cells using conventional CR2032 coin cell preparation methods. Battery performance was tested, with a charge / discharge voltage range of 0-3V. See Table 1 for details. Figure 2 .

[0166] Table 1: Battery performance data of coin cells made from coal-based anode materials obtained in Examples 1 to 5 and Comparative Examples 1 to 7.

[0167]

[0168]

[0169] From Table 1 and Figure 2 As can be seen, the overall performance of the coin cells prepared using the coal-based anode materials of Examples 1 to 5 is superior to that of the coin cells prepared using the coal-based anode materials of Comparative Examples 1 to 7. This demonstrates that, under the microwave power and processing time specified in this application, using coal-based anode materials obtained by further processing coal-based raw materials with N-methylpyrrolidone in sodium-ion batteries can effectively improve the reversible specific capacity and cycle performance of sodium-ion batteries. Furthermore, please refer to... Figures 2 to 5 In particular, when anthracite, coking coal and lignite are used in combination as coal-based raw materials to obtain coal-based anode materials for sodium-ion batteries, the reversible specific capacity and cycle performance of sodium-ion batteries are better. Moreover, the disorder of the coal-based anode material is significantly changed, which increases the interlayer spacing of the coal-based raw materials, thereby improving the reversible specific capacity and cycle performance of sodium-ion batteries.

[0170] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a sodium-ion battery anode material, characterized in that, Includes the following steps: Obtaining coal-based raw materials; The coal-based raw material is subjected to a defect-enhancing process to induce oxidative cross-linking, thereby obtaining a pre-oxidized coal-based anode material. The pre-oxidized coal-based anode material is subjected to thermal extraction treatment to remove organic impurities from the pre-oxidized coal-based anode material; The pre-oxidized coal-based anode material after thermal extraction is subjected to high-temperature doping, with the temperature raised to 1000℃~1500℃ during the high-temperature doping process, to obtain a sodium-ion battery anode material. Specifically, the defect-reducing operation on the coal-based raw material involves microwave heat treatment of the coal-based raw material under oxygen conditions. The coal-based raw material is subjected to microwave heat treatment, specifically as follows: the coal-based raw material is placed in a microwave oven and microwaved for 0.8 min to 1.2 min at a microwave power of 180 W to 220 W; then microwaved for 0.8 min to 1.2 min at a microwave power of 350 W to 420 W; then microwaved for 0.8 min to 1.2 min at a microwave power of 580 W to 650 W; then microwaved for 1.6 min to 2.0 min at a microwave power of 950 W to 1200 W; and finally microwaved for 4.8 min to 5.5 min at a microwave power of 1500 W to 1800 W. The pre-oxidized coal-based anode material was subjected to thermal extraction treatment using an organic solvent; The organic solvent is N-methylpyrrolidone.

2. The method for preparing the sodium-ion battery negative electrode material according to claim 1, characterized in that, The coal-based raw materials include at least one of anthracite, bituminous coal, coking coal, and lignite.

3. The method for preparing the sodium-ion battery negative electrode material according to claim 1, characterized in that, The pre-oxidized coal-based anode material after thermal extraction is subjected to high-temperature doping, including the following steps: Obtain the dopant source; The doping source and the pre-oxidized coal-based negative electrode material are placed at the inlet and outlet respectively. Inert gas is introduced into the inlet and the inert gas flows to the outlet. The doping source and the pre-oxidized coal-based anode material are subjected to heat treatment by heating.

4. The method for preparing the sodium-ion battery negative electrode material according to claim 3, characterized in that, The doping source includes at least one of elemental sulfur, elemental phosphorus, tin sulfide, and antimony sulfide.

5. The method for preparing the sodium-ion battery negative electrode material according to claim 3, characterized in that, The flow rate of the inert gas is 100 mL / min to 200 mL / min.

6. The method for preparing the sodium-ion battery negative electrode material according to claim 3, characterized in that, The doped source and the pre-oxidized coal-based anode material are subjected to heat treatment by heating to 1000℃~1500℃ at a heating rate of 5℃ / min~8℃ / min, and then held at the temperature for 5 h~8 h.

7. A sodium-ion battery anode material, characterized in that, The sodium-ion battery anode material is prepared by any one of the preparation methods of claims 1 to 6.

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