Universal method for preparing hard carbon material

Abstract

The invention discloses a universal method for preparing a hard carbon material, which comprises the following steps: treating a biomass raw material, and putting the biomass raw material into a strong base KOH solution for soaking treatment to destroy organic matter molecules in the biomass raw material to obtain the biomass raw material; putting the treated biomass raw material into a tubular furnace in a nitrogen atmosphere, raising the temperature from room temperature to 200 DEG C, then carrying out preheating treatment for 2 hours in an inert atmosphere of 200 DEG C, dehydrating and softening the material; and along with the completion of preheating dehydration, heating the tubular furnace to 1200 DEG C, preserving heat for 2 hours, and naturally cooling after the completion of heat preservation, thereby obtaining the hard carbon material. According to the invention, the hard carbon material with a long-range disordered and short-range ordered hard carbon material characteristic structure can be prepared, the interlayer spacing of the hard carbon material is greater than 0.37 nm, the hard carbon material is more suitable for being used as a negative electrode material of a sodium ion battery or a lithium ion battery, and the applicable biomass raw materials are diversified, high in universality and higher in universality.

Description

Technical Field

[0001] The invention relates to the technical field of hard carbon material preparation, and in particular to a universal method for preparing hard carbon material. Background Art

[0002] With the increasing contradiction between energy demand and increasingly serious environmental problems, the development of clean energy has become a social consensus. The development of lithium batteries has now provided a feasible option for social development, but there is still a lot of room for improvement in the service life of lithium batteries. Among them, hard carbon materials, as potential application materials to replace activated carbon materials, have long cycle life, good power performance, and less expansion caused by the embedding of lithium ions and sodium ions; they have very obvious advantages. Therefore, the preparation of hard carbon is of great significance.

[0003] At present, in some methods, such as the use of chlorinated hydrocarbons as raw materials in patent CN 114361389 A and the use of resorcinol as raw materials in patent CN108899542 A, although the performance of the synthetic hard carbon is also better than that of graphite, the raw materials used in its production are mainly chemical raw materials, which are relatively low in both environmental pressure and economic cost; therefore, the method of synthesizing hard carbon using biomass has great potential. In the materials for synthesizing hard carbon from biomass, such as patent CN 112661133A, its biomass materials are limited to coconut shells, and there is no possibility of further expanding its application, which limits its use; for example, patent CN 111564630 A only uses orange peel as its raw material for preparation; it is not difficult to see from the previous patents that everyone has not developed a method for preparing hard carbon from a variety of biomass materials; therefore, it is very economically valuable to develop a preparation method that can be applied to a variety of biomass hard carbon materials.

[0004] Based on the above, we proposed a universal method for preparing hard carbon materials. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a universal method for preparing hard carbon materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A general method for preparing hard carbon material comprises the following steps: S1: Strong alkali pretreatment The biomass raw material is placed in a strong alkaline KOH solution for soaking treatment to destroy the organic molecules in the biomass raw material to obtain the biomass raw material; S2: Initial warming The biomass raw material treated in step S1 is placed in a tubular furnace in a nitrogen atmosphere, and the temperature is raised from room temperature to 200°C, and then preheated at 200°C in an inert atmosphere for 2 h to dehydrate and soften the material; S3: Secondary heating With the completion of the preheating and dehydration in step S2, the temperature of the tubular furnace is raised to 1200°C and kept at this temperature for 2 hours under the protection of the inert atmosphere in step S2. After the end of the keeping temperature, the temperature is naturally lowered to prepare the hard carbon material.

[0007] Preferably, the biomass raw materials include multiple types, specifically any one of glucose, cellulose, bagasse, bamboo powder, spruce powder, oak powder, alkali lignin, soybean straw, wheat straw, barley ears, green tea powder, pollen, walnut shells, dandelion powder, rapeseed pollen, orange peel, tangerine peel, and gardenia.

[0008] Preferably, the concentration of the strong base KOH solution is 5%.

[0009] Preferably, in steps S2 and S3, the heating rates during the process of heating the room temperature to 200°C and from 200°C to 1200°C are both 5°C / min.

[0010] The present invention provides a general method for preparing hard carbon materials, which has the following beneficial effects: 1. The present invention can prepare a hard carbon material with a characteristic structure of long-range disorder and short-range order through a strong alkali pretreatment process, and its interlayer spacing is greater than 0.37 nm, which is more conducive to the embedding and extraction of sodium ions and lithium ions, and is therefore more suitable for use as a negative electrode material for sodium ion batteries or lithium ion batteries.

[0011] 2. The biomass raw materials that can be used in the present invention are diverse, have strong versatility, and have greater universality. The present invention can effectively utilize biomass materials to prepare hard carbon and has higher economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the XRD pattern of hard carbon prepared from biomass materials in Example 2 of the present invention.

[0013] Figure 2 This is the XRD pattern of hard carbon prepared from biomass materials in Experimental Example 1 of the present invention. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Embodiment 1

[0015] A general method for preparing hard carbon material comprises the following steps: S1: Strong alkali pretreatment The biomass raw material is placed in a 5% strong alkaline KOH solution for soaking to destroy the organic molecules in the biomass raw material to obtain the biomass raw material; S2: Initial warming The biomass raw material treated in step S1 is placed in a tubular furnace in a nitrogen atmosphere, and the temperature is raised from room temperature to 200°C at a rate of 5°C / min, and then preheated at 200°C in an inert atmosphere for 2 h to dehydrate and soften the material; S3: Secondary heating With the completion of the preheating and dehydration in step S2, under the protection of the inert atmosphere based on step S2, the tube furnace is heated to 1200°C at a heating rate of 5°C / min and kept at this temperature for 2 h. After the insulation is completed, the temperature is naturally lowered to obtain the hard carbon material.

[0016] The biomass raw materials in the above embodiment include multiple types, specifically any one of glucose, cellulose, bagasse, bamboo powder, spruce powder, oak powder, alkali lignin, soybean straw, wheat straw, barley ears, green tea powder, pollen, walnut shells, dandelion powder, rapeseed pollen, orange peel, tangerine peel, and gardenia.

[0017] Example 2, based on the above Example 1, soybean straw, wheat straw, barley ear, green tea powder, pollen, walnut shell, dandelion powder, rapeseed pollen, orange peel, tangerine peel, gardenia are selected to prepare the corresponding hard carbon materials, and the obtained hard carbon materials are tested for structure by X-ray diffraction (XRD). The test results are as follows: Figure 1 shown.

[0018] Based on this, the biomass raw materials that can be used in the present invention are diverse, have strong versatility, have greater universality, can effectively utilize biomass materials to prepare hard carbon, and have higher economic value.

[0019] Test Example 1 Based on the above examples, three groups of cellulose hard carbon materials, bamboo powder hard carbon materials, and oak powder hard carbon materials were prepared, namely group A, group B, and group C. The cellulose hard carbon material, bamboo powder hard carbon material, and oak powder hard carbon material of group A are obtained by traditional hard carbon preparation process; The cellulose hard carbon material, bamboo powder hard carbon material, and oak powder hard carbon material of group B are prepared by the present process but with a strong base KOH solution of 0.5%; The cellulose hard carbon material, bamboo powder hard carbon material and oak powder hard carbon material of group C are prepared by the present process but with a strong alkaline KOH solution of 5%.

[0020] The hard carbon materials obtained from Group A, Group B, and Group C were subjected to structural testing by X-ray diffraction (XRD). The test results are as follows: Figure 1 As shown, it can be seen from the figure that the material has met the standards of hard carbon.

[0021] Based on this, the present invention solves the problem that the traditional hard carbon preparation process has only a simple carbonization process but no pretreatment process, resulting in a small hard carbon layer and no utilization of lithium ions, especially the embedding and extraction of sodium ions, through a strong alkali pretreatment process. Thus, a hard carbon material with a long-range disordered and short-range ordered hard carbon material characteristic structure can be prepared, and its interlayer spacing is greater than 0.37 nm, which is more conducive to the embedding and extraction of sodium ions and lithium ions, and is therefore more suitable for use as a negative electrode material for sodium ion batteries or lithium ion batteries.

[0022] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A general method for preparing hard carbon materials, characterized in that: The steps include: S1: Strong alkali pretreatment The biomass raw material is placed in a strong alkaline KOH solution for soaking treatment to destroy the organic molecules in the biomass raw material to obtain the biomass raw material; S2: Initial warming The biomass raw material treated in step S1 is placed in a tubular furnace in a nitrogen atmosphere, and the temperature is raised from room temperature to 200°C, and then preheated at 200°C in an inert atmosphere for 2 h to dehydrate and soften the material; S3: Secondary heating With the completion of the preheating and dehydration in step S2, the temperature of the tubular furnace is raised to 1200°C and kept at this temperature for 2 hours under the protection of the inert atmosphere in step S2. After the end of the keeping temperature, the temperature is naturally lowered to prepare the hard carbon material.

2. A general method for preparing hard carbon materials according to claim 1, characterized in that: The biomass raw materials include multiple types, specifically any one of glucose, cellulose, bagasse, bamboo powder, spruce powder, oak powder, alkali lignin, soybean straw, wheat straw, barley ears, green tea powder, pollen, walnut shells, dandelion powder, rapeseed pollen, orange peel, tangerine peel, and gardenia.

3. A general method for preparing hard carbon materials according to claim 1, characterized in that: The concentration of the strong base KOH solution is 5%.

4. A general method for preparing hard carbon materials according to claim 1, characterized in that: In steps S2 and S3, the heating rates from room temperature to 200°C and from 200°C to 1200°C are both 5°C / min.

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