Biomass waste wood chip derived carbon negative electrode material and preparation method thereof, lithium ion battery and electric device

Abstract

The invention discloses a biomass waste wood chip derived carbon negative electrode material and a preparation method thereof, a lithium ion battery and an electric device. The preparation method comprises the following steps: pre-carbonizing biomass waste wood chips, and then mixing a pre-carbonized sample and an activating agent according to different mass ratios to obtain a mixed material; performing high-temperature activation treatment on the mixed material and a pore-enlarging agent under the protection of inert gas to obtain an activated sample; the activated sample is washed with an acid solution and water, finally, the porous carbon electrode material is obtained, simple, low-cost, environment-friendly and efficient wood chips are adopted as a carbon source, and resource utilization of waste is achieved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a carbon anode material derived from biomass waste wood chips, its preparation method, a lithium-ion battery, and an electrical device thereof. Background Technology

[0002] Lithium-ion batteries are widely used in various energy storage fields due to their high energy density and long cycle life. Graphite is the most commonly used anode material for lithium-ion batteries; however, graphite exhibits low power, low energy density, and low performance, and its theoretical capacity is approaching its theoretical limit, making further performance improvement difficult. Besides commercial graphite and hard and soft carbon, graphite and carbon nanotubes, as novel carbon materials, have been extensively studied due to their abundant active sites, good conductivity, and high porosity. However, most high-performance carbon anode materials are synthesized from non-renewable fossil fuels using complex methods. Therefore, developing and preparing inexpensive and environmentally friendly carbon materials that are simple to synthesize and have excellent performance is crucial. Biomass, as a renewable energy source on Earth, has advantages such as low cost, ease of acquisition, and the reduced aromatic structure of biomass pyrolysis products, which is conducive to the formation of porous structures. It has played an excellent role in developing sustainable biomass-derived carbon and its composite materials to achieve high-performance lithium-ion battery anode materials. Due to its large specific surface area, high physicochemical stability, and good conductivity, it is considered a potential material for lithium-ion battery anode materials.

[0003] The microporous structure of porous carbon provides storage space for lithium ions, which not only shortens the lithium ion transport path but also creates a larger electrolyte interface for charge transfer reactions. In other words, the large specific surface area and stable structure of carbon materials can improve their conductivity and cycle stability. Furthermore, doping heteroatoms into the carbon framework is an effective method to improve the electrochemical performance of porous carbon materials. This modification can alter the pore structure of carbon materials, thereby shortening ion / charge transport and diffusion paths. In addition, it enhances the surface chemical and electronic properties of carbon materials, resulting in more lithium ion storage active sites and defects, and improving the conductivity of carbon materials.

[0004] Wood chips, a type of biomass waste, possess abundant lignocellulose and numerous ordered pore structures, making them suitable templates for synthesizing high-porosity materials. Furthermore, as an agricultural waste, wood chips are readily available and inexpensive. These factors contribute to the excellent scalability and cost-effectiveness of biomass waste, making it an ideal raw material for lithium-ion batteries. However, biomass-derived carbon materials face significant challenges in becoming anode materials for lithium-ion batteries, primarily due to complex preparation processes, limited porosity, and insufficient rate performance.

[0005] Currently, to address the need for waste resource utilization and the demand for anodes in high-energy-density batteries, porous carbon derived from biomass waste wood chips has been prepared using a carbonization activation method. Its large specific surface area and heteroatom doping provide abundant storage sites, while the porous structure (micropores and mesopores) promotes rapid ion transport. However, porous carbon, as an anode material for lithium-ion batteries, suffers from low lithium storage efficiency due to its unreasonable pore size distribution, making it difficult to achieve efficient electrochemical energy storage. Secondly, its initial coulombic efficiency is generally low, attributed to the large amount of irreversible lithium dissipation caused by the porous structure and the formation of an excessively thick solid electrolyte interphase (SEI) film. Furthermore, the material's low compaction density severely limits the battery's energy density, affecting overall performance. Finally, traditional preparation processes such as high-temperature activation and chemical etching are not only energy-intensive but also pose environmental pollution risks, hindering its large-scale production and practical application. Current methods for preparing porous carbon produce materials with uneven pore distribution, and it is difficult to prepare excellent porous carbon materials using a single activator. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, embodiments of the present invention provide a carbon anode material derived from biomass waste wood chips, a method for preparing the same, a lithium-ion battery, and an electrical device thereof.

[0008] In a first aspect, the present invention proposes a method for preparing a carbon anode material derived from biomass waste wood chips, comprising the following steps: (1) The sawdust was crushed, sieved, washed and dried, and then pre-carbonized to obtain a pre-carbonized sample; (2) After mixing the pre-carbonized sample with the activator, deionized water is added and stirred to dissolve the activator. Then, the mixture is heated and dried to remove moisture to obtain the mixture. (3) The mixture is ground and mixed with a pore-expanding agent and then calcined to obtain an activated sample; (4) The activated sample is washed, dried and then ground to obtain porous carbon material.

[0009] Furthermore, the mass ratio of the pre-carbonized sample to the activator is 1:(2~4).

[0010] Further, the mass ratio of the mixture to the pore-expanding agent is 1:(0.1~0.3).

[0011] Furthermore, the activator includes one or more of KOH, KHCO3, KMnO4, K2CO3, and H3PO4.

[0012] Furthermore, the pore-expanding agent includes one or more of urea, thiourea, diammonium hydrogen phosphate, and ammonium sulfate.

[0013] Furthermore, in step (1), the wood chips are crushed and then passed through a 40-70 mesh sieve.

[0014] Furthermore, the drying temperature in step (1) is 80~100℃ and the time is 6~12h.

[0015] Furthermore, the pre-carbonization treatment in step (1) is to heat at 200~400℃ for 1~3h under an inert gas.

[0016] Furthermore, the drying temperature in step (2) is 100~120℃ and the time is 2~4h.

[0017] Furthermore, in step (3), calcination is performed by heating at 600~900℃ for 1~4 hours under an inert gas atmosphere.

[0018] Furthermore, in step (4), the drying temperature is 60~100℃ and the drying time is 24~36h.

[0019] Furthermore, the specific surface area of ​​the porous carbon material is 1700 m². 2 / g or more.

[0020] Furthermore, the particle size of the porous carbon material is 0.1~10 nm.

[0021] Secondly, the present invention provides a negative electrode material prepared by the method proposed in the first aspect above.

[0022] Thirdly, the present invention provides a lithium-ion battery, including a negative electrode sheet, wherein the negative electrode sheet includes a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector, wherein the negative electrode active material includes the negative electrode material proposed in the second aspect above.

[0023] Fourthly, the present invention provides an electrical device comprising the lithium-ion battery described in the third aspect above.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The porous carbon prepared by this invention has a high specific surface area and abundant micropores and mesopores. When used as a negative electrode material for lithium-ion batteries, the multi-level porous carbon has important functional advantages. The microporous structure can provide a large number of active sites and storage space to accommodate more lithium ions, which is beneficial to charge storage. The mesoporous structure shortens the ion transport distance and is a diffusion transport channel for rapid lithium ion insertion and extraction, thus accelerating ion transport.

[0025] The preparation process of this invention is simple, and the raw material used, biomass waste wood chips, is inexpensive and suitable for mass production, thus realizing the resource utilization of waste. Attached Figure Description

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart illustrating the preparation method of the carbon anode material derived from biomass waste wood chips according to the present invention. Detailed Implementation

[0027] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0028] The following description, in conjunction with the accompanying drawings, describes the biomass waste wood chip-derived carbon anode material, its preparation method, lithium-ion battery, and electrical device proposed in this invention.

[0029] like Figure 1 As shown, the preparation method of the biomass waste wood chip-derived carbon anode material of the present invention includes the following steps: (1) The sawdust was crushed, sieved, washed and dried, and then pre-carbonized to obtain a pre-carbonized sample; (2) After mixing the pre-carbonized sample with the activator, add deionized water and stir to dissolve the activator. Then heat and dry to remove moisture to obtain the mixture. (3) The mixture is ground and mixed with the pore-expanding agent and then calcined to obtain an activated sample; (4) After washing and drying the activated sample, grind it to obtain porous carbon material.

[0030] Step (1) involves pre-treating the wood chips to obtain a pre-carbonized sample. Specifically, the wood chips are crushed, passed through a 40-70 mesh sieve, washed with deionized water to remove surface impurities, and dried. The dried wood chips are then pre-carbonized to obtain the pre-carbonized sample. The pre-carbonization process of this invention allows for thorough mixing of the raw materials, reduces the dehydration rate of the biomass carbon material during subsequent high-temperature calcination, and facilitates the formation of a more uniform pore structure.

[0031] In some embodiments, the drying temperature is 80~100°C and the drying time is 6~12h. It is understood that the drying temperature can be 80°C, 90°C, 100°C or any combination of two values, and the drying time can be 6h, 8h, 10h, 12h or any combination of two values.

[0032] In some embodiments, the pre-carbonization treatment involves heating at 200-400°C for 1-3 hours under an inert gas. It is understood that the heating temperature for the pre-carbonization treatment can be 200°C, 300°C, 400°C, or any combination of two values, and the heating time can be 1 hour, 2 hours, 3 hours, or any combination of two values. The inert gas can be nitrogen or argon.

[0033] Step (2) involves mixing the pre-carbonized sample obtained in step (1) with the activator. After mixing the pre-carbonized sample and the activator at a certain mass ratio, an appropriate amount of deionized water is added. The mixture is stirred at room temperature for a certain period of time to completely dissolve the activator. Then, it is dried at a certain temperature to ensure that the moisture is completely removed and a mixture is obtained. The activator is added to allow it to react chemically with the carbon skeleton during subsequent high-temperature calcination, ultimately etching out pores.

[0034] In some embodiments, the mass ratio of the pre-carbonized sample to the activator is 1:(2~4). It is understood that the mass ratio of the pre-carbonized sample to the activator can be 1:2, 1:3, 1:4 or any value within the range of any two values. If the activator content is too high, the carbon surface will be over-etched, resulting in pore collapse. If the activator content is too low, the material will not be sufficiently activated and will not be able to fully penetrate into the internal structure of the material.

[0035] In some embodiments, the activator includes one or more of KOH, KHCO3, KMnO4, K2CO3, and H3PO4.

[0036] In some embodiments, the drying temperature for removing moisture is 100~120℃ and the time is 2~4h. It can be understood that the drying temperature can be 100, 110, 120℃ or any two of these values, and the drying time can be 2h, 3h, 4h or any two of these values.

[0037] Step (3) involves grinding and mixing the mixture prepared in step (2) with a pore expander and then calcining it to obtain an activated sample. First, the mixture and the pore expander are mixed in a certain mass ratio and ground to ensure thorough mixing. Then, the sample is calcined under an inert gas to obtain an activated sample.

[0038] In some embodiments, the mass ratio of the mixture to the pore expander is 1:(0.1~0.3). It is understood that the mass ratio of the mixture to the pore expander can be 1:0.1, 1:0.2, 1:0.3, or any value within a range of two such values. The addition of the pore expander induces higher density defects and disorder in the carbon material during the activation process. Excessive pore expander content can affect the pore structure, causing blockage of existing pores; insufficient pore expander content prevents it from fully penetrating the material and participating in the reaction.

[0039] In some embodiments, the pore-expanding agent includes one or more of urea, thiourea, diammonium hydrogen phosphate, and ammonium sulfate.

[0040] In some embodiments, calcination is performed by heating at 600~900°C for 1~4 hours. During the calcination process, most of the pore expander decomposes and vaporizes. In addition, the activator also releases gas at high temperature, generating additional pores. The combination of the pore expander and the activator forms a layered pore network structure with the synergistic effect of micropores and mesopores.

[0041] Understandably, the calcination temperature can be 600℃, 700℃, 800℃, 900℃ or any combination of two values, and the calcination time can be 1h, 2h, 3h, 4h or any combination of two values.

[0042] In this invention, during the high-temperature carbonization and activation stage, the pore-forming agent and the activator can react with carbon, and the natural pore structure of biomass waste wood chips provides a basic framework for the pore-forming process. The synergistic effect of the two allows pore-forming and activation to proceed simultaneously, thereby preparing biomass porous carbon materials.

[0043] In step (4), the activated sample obtained in step (3) is washed multiple times with acid solution and deionized water until neutral. Then the activated sample is dried and ground to a certain mesh size to obtain a porous carbon material with micropores, mesopores and hierarchical pore structures.

[0044] In some embodiments, the acid solution is dilute hydrochloric acid or dilute phosphoric acid. The purpose of washing with the acid solution is mainly to remove residual ash and impurities from the preparation process, that is, to remove amorphous carbon and impurities that clog the pore structure and clean the pores.

[0045] In some embodiments, the drying temperature is 60~100℃ and the drying time is 24~36h. It is understood that the drying temperature can be 60℃, 70℃, 80℃, 90℃, 100℃ or any two of these values, and the drying time can be 24h, 28h, 30h, 32h, 36h or any two of these values.

[0046] In some embodiments, the specific surface area of ​​the porous carbon material is 1700 m². 2 The porous carbon material, with a particle size of 0.1~10 nm and a density of over / g, primarily exhibits microporous and mesoporous structures. When used as a negative electrode material for lithium-ion batteries, the porous carbon material of this invention has a large specific surface area and abundant micropores and mesopores, allowing for sufficient permeation between the electrode material and the electrolyte, thereby shortening the lithium-ion diffusion path. Furthermore, the high specific surface area and pore volume of the mesoporous material can accelerate the transport of ions and electrons, thereby improving the electrochemical performance of the material.

[0047] This invention pre-carbonizes biomass waste wood chips, then mixes the pre-carbonized sample with an activator at different mass ratios to obtain a mixture; the mixture and a pore-expanding agent are then subjected to high-temperature activation treatment under inert gas protection to obtain an activated sample; the activated sample is then washed with acid solution and water to finally obtain a porous carbon electrode material. By using simple, low-cost, environmentally friendly, and efficient wood chips as a carbon source, the resource utilization of waste is achieved.

[0048] This invention uses inexpensive activators and a simple mixing method to prepare high-performance porous carbon electrode materials on a large scale, quickly and efficiently, effectively reducing the preparation cost of porous carbon anode materials and making them suitable for large-scale production.

[0049] The pore-expanding agent of this invention can effectively adjust the pore structure of porous carbon, which is beneficial to obtaining a richer pore structure. The microporous structure of porous carbon can provide storage space for lithium ions, which not only shortens the lithium ion transport path but also creates a larger electrolyte interface for charge transfer reactions. The large specific surface area and stable structure of carbon materials can improve their conductivity and cycle stability.

[0050] The negative electrode material of this invention is prepared by the method for preparing carbon negative electrode material derived from biomass waste wood chips. The lithium-ion battery of this invention includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector; the negative electrode active material is the negative electrode material of this invention. The electrical device of this invention includes the lithium-ion battery of this invention.

[0051] The present invention will now be described in detail with reference to specific embodiments.

[0052] Example 1 Preparation of porous carbon materials: The sawdust was crushed and passed through a 50-mesh sieve, washed with deionized water, and dried at 90°C for 8 hours to remove surface impurities. A certain amount of the dried sawdust sample was heated at 200°C for 3 hours in an inert gas atmosphere to obtain a pre-carbonized sample.

[0053] The pre-carbonized sample was mixed with the activator, and an appropriate amount of deionized water was added to completely dissolve the activator. The mixed slurry was then dried at 100°C for 4 hours to ensure complete removal of moisture, yielding the final mixture. The activator was KOH, and the mass ratio of the pre-carbonized sample to the activator was 1:2.

[0054] The mixture and pore-expanding agent were thoroughly ground and mixed, then calcined at 600°C for 3 hours under an argon atmosphere to obtain an activated sample. The pore-expanding agent was thiourea, and the mass ratio of the mixture to the pore-expanding agent was 1:0.2. In this embodiment, thiourea was used as an NS co-doperbide, which reacts with the oxygen-containing functional groups of lignocellulose during the activation process, generating a large number of micropores. During high-temperature activation, the activation effect of the activating agent KOH further expanded the micropores into more mesopores and micropores.

[0055] The activated sample was washed with 1M dilute hydrochloric acid and deionized water until neutral. Then, the activated sample was placed in an oven and dried at 80°C for 24 hours. The dried sample was then ground to a certain mesh size to obtain porous carbon material.

[0056] The fabrication of lithium-ion batteries: Porous carbon, conductive carbon black, and polyvinylidene fluoride were mixed evenly in a mass ratio of 8:1:1. A certain amount of N-methylpyrrolidone was added, and the mixture was stirred evenly to obtain a slurry. The slurry was coated onto copper foil and dried in a vacuum drying oven at 90°C for 12 hours to obtain the negative electrode sheet.

[0057] A lithium metal sheet was used as the counter electrode. The electrolyte was a 1 mol / L mixture of LiPF6 (lithium hexafluorophosphate) and EC (ethylene carbonate):DMC (dimethyl carbonate):EMC (ethyl methyl carbonate) in a 1:1:1 volume ratio. A PP (polypropylene film) membrane was used as the separator. The lithium-ion coin cells were assembled in a glove box. After being left to stand for a certain period, electrochemical tests were performed, and the capacity was measured at a current density of 0.1 A / g.

[0058] Example 2 Preparation of porous carbon materials: The sawdust was crushed and passed through a 40-mesh sieve, washed with deionized water, and dried at 100°C for 6 hours to remove surface impurities. A certain amount of the dried sawdust sample was heated at 200°C for 3 hours in an inert gas atmosphere to obtain a pre-carbonized sample.

[0059] The pre-carbonized sample was mixed with the activator, and an appropriate amount of deionized water was added to completely dissolve the activator. The mixed slurry was then dried at 100°C for 4 hours to ensure complete removal of moisture, yielding the final mixture. The activator was H3PO4, and the mass ratio of the pre-carbonized sample to the activator was 1:3.

[0060] The mixture and pore-expanding agent were thoroughly ground and mixed, then calcined at 600°C for 3 hours under an argon atmosphere to obtain an activated sample. The pore-expanding agent was diammonium hydrogen phosphate, and the mass ratio of the mixture to the pore-expanding agent was 1:0.3. In this example, NH4... +As the H3PO4 impregnation gradually penetrates into the internal structure of the biomass wood chips, some chemical reactions occur during the heat treatment process, resulting in the release of abundant gaseous products (NH3 and other gaseous products), opening up a large number of closed pores.

[0061] The activated sample was washed with 1M dilute hydrochloric acid and deionized water until neutral. Then, the activated sample was placed in an oven and dried at 80°C for 24 hours. The dried sample was then ground to a certain mesh size to obtain porous carbon material.

[0062] The other processes are the same as in Example 1.

[0063] Example 3 Preparation of porous carbon materials: The sawdust was crushed and passed through a 50-mesh sieve, washed with deionized water, and dried at 100°C for 6 hours to remove surface impurities. A certain amount of the dried sawdust sample was heated at 200°C for 3 hours in an inert gas atmosphere to obtain a pre-carbonized sample.

[0064] The pre-carbonized sample was mixed with the activator, and an appropriate amount of deionized water was added to completely dissolve the activator. The mixed slurry was then dried at 100°C for 4 hours to ensure complete removal of moisture, yielding the final mixture. The activator was H3PO4, and the mass ratio of the pre-carbonized sample to the activator was 1:3.

[0065] The mixture and the pore-expanding agent were thoroughly ground and mixed, and then calcined at 900℃ for 1 hour under an argon atmosphere to obtain an activated sample. The pore-expanding agent was ammonium sulfate, and the mass ratio of the mixture to the pore-expanding agent was 1:0.3.

[0066] The activated sample was washed with 1M dilute hydrochloric acid and deionized water until neutral. Then, the activated sample was placed in an oven and dried at 80°C for 24 hours. The dried sample was then ground to a certain mesh size to obtain porous carbon material.

[0067] The other processes are the same as in Example 1.

[0068] Example 4 Preparation of porous carbon materials: The sawdust was crushed and passed through a 50-mesh sieve, washed with deionized water, and dried at 90°C for 8 hours to remove surface impurities. A certain amount of the dried sawdust sample was heated at 300°C for 2 hours in an inert gas atmosphere to obtain a pre-carbonized sample.

[0069] The pre-carbonized sample was mixed with the activator, and an appropriate amount of deionized water was added to completely dissolve the activator. The mixed slurry was then dried at 100°C for 4 hours to ensure complete removal of moisture, yielding the final mixture. The activator was KMnO4, and the mass ratio of the pre-carbonized sample to the activator was 1:4.

[0070] The mixture and pore-expanding agent were thoroughly ground and mixed, then calcined at 600°C for 3 hours under an argon atmosphere to obtain an activated sample. The pore-expanding agent was urea, and the mass ratio of the mixture to the pore-expanding agent was 1:0.1. In this embodiment, treatment with potassium permanganate solution enhances ion exchange through acid-base neutralization, allowing more alkali metal ions to enter the precursor surface. Furthermore, removing the alkali metal from the graphite layer of the carbon material after high-temperature activation leaves a uniform porous structure on the carbon material surface.

[0071] The activated sample was washed with 1M dilute hydrochloric acid and deionized water until neutral. Then, the activated sample was placed in an oven and dried at 60°C for 36 hours. The dried sample was then ground to a certain mesh size to obtain porous carbon material.

[0072] The other processes are the same as in Example 1.

[0073] Example 5 Preparation of porous carbon materials: The sawdust was crushed and passed through a 50-mesh sieve, washed with deionized water, and dried at 90°C for 8 hours to remove surface impurities. A certain amount of the dried sawdust sample was heated at 200°C for 3 hours in an inert gas atmosphere to obtain a pre-carbonized sample.

[0074] The pre-carbonized sample was mixed with the activator, and an appropriate amount of deionized water was added to completely dissolve the activator. The mixed slurry was then dried at 100°C for 4 hours to ensure complete removal of moisture, yielding the final mixture. The activator was KHCO3, and the mass ratio of the pre-carbonized sample to the activator was 1:3.

[0075] The mixture and the pore-expanding agent were thoroughly ground and mixed, and then calcined at 600℃ for 3 hours under an argon atmosphere to obtain an activated sample. The pore-expanding agent was thiourea, and the mass ratio of the mixture to the pore-expanding agent was 1:0.3.

[0076] The activated sample was washed with 1M dilute hydrochloric acid and deionized water until neutral. Then, the activated sample was placed in an oven and dried at 80°C for 24 hours. The dried sample was then ground to a certain mesh size to obtain porous carbon material.

[0077] The other processes are the same as in Example 1.

[0078] Comparative Example 1 Preparation of porous carbon materials: The sawdust was crushed and passed through a 50-mesh sieve, washed with deionized water, and dried at 90°C for 8 hours to remove surface impurities. A certain amount of the dried sawdust sample was heated at 200°C for 3 hours in an inert gas atmosphere to obtain a pre-carbonized sample.

[0079] The pre-carbonized sample was calcined at 600℃ for 3 hours under an argon atmosphere to obtain carbon material.

[0080] The other processes are the same as in Example 1.

[0081] Comparative Example 2 Preparation of porous carbon materials: The sawdust was crushed and passed through a 50-mesh sieve, washed with deionized water, and dried at 90°C for 8 hours to remove surface impurities. A certain amount of the dried sawdust sample was heated at 200°C for 3 hours in an inert gas atmosphere to obtain a pre-carbonized sample.

[0082] The pre-carbonized sample was mixed with the activator, and an appropriate amount of deionized water was added to completely dissolve the activator. The mixed slurry was then dried at 100°C for 4 hours to ensure complete removal of moisture, yielding the final mixture. The activator was KOH, and the mass ratio of the pre-carbonized sample to the activator was 1:2.

[0083] The mixture was calcined at 600°C for 3 hours under an argon atmosphere to obtain an activated sample.

[0084] The activated sample was washed with 1M dilute hydrochloric acid and deionized water until neutral. Then, the activated sample was placed in an oven and dried at 80°C for 24 hours. The dried sample was then ground to a certain mesh size to obtain porous carbon material.

[0085] The other processes are the same as in Example 1.

[0086] Comparative Example 3 Preparation of porous carbon materials: The sawdust was crushed and passed through a 50-mesh sieve, washed with deionized water, and dried at 90°C for 8 hours to remove surface impurities. A certain amount of the dried sawdust sample was heated at 200°C for 3 hours in an inert gas atmosphere to obtain a pre-carbonized sample.

[0087] The pre-carbonized sample and the pore-expanding agent were thoroughly ground and mixed, and then calcined at 600℃ for 3 hours under an argon atmosphere to obtain the activated sample. The pore-expanding agent was thiourea, and the mass ratio of the pre-carbonized sample to the pore-expanding agent was 1:0.2.

[0088] The activated sample was washed with 1M dilute hydrochloric acid and deionized water until neutral. Then, the activated sample was placed in an oven and dried at 80°C for 24 hours. The dried sample was then ground to a certain mesh size to obtain porous carbon material.

[0089] The other processes are the same as in Example 1.

[0090] Comparative Example 4 The difference from Example 1 is that the mass ratio of the pre-carbonized sample to the activator is 1:6. The other processes are the same as in Example 1.

[0091] Comparative Example 5 The difference from Example 1 is that the mass ratio of the mixture to the pore-expanding agent is 1:0.5. The other processes are the same as in Example 1.

[0092] Experimental Example 1 The carbon materials of Examples 1-5 and Comparative Examples 1-5 were tested for specific surface area and specific volume, and the test results are shown in Table 1 below. Simultaneously, the lithium-ion batteries of Examples 1-5 and Comparative Examples 1-5 were tested for reversible specific capacity, capacity retention after 100 cycles, and capacity retention after 500 cycles, and the test results are shown in Table 1 below.

[0093] Among them, the reversible specific capacity test involves electrochemical testing after the lithium-ion coin cell has been left to stand for a certain period of time, and its capacity is tested at a current density of 0.1 A / g.

[0094] The capacity retention rate test method was as follows: The electrochemical performance of the assembled lithium-ion batteries was tested using a Wuhan Landian CT 3002A battery testing system (LAND, China). The tests were conducted at a constant temperature of 25℃, with a voltage range of 0.01~3.0V (vs. Li). + Using / Li as the voltage window, the battery performance is evaluated using a constant current charge-discharge mode.

[0095] Table 1:

[0096] According to Table 1: Compared with Comparative Examples 1-5, the carbon materials of Examples 1-5 have a larger specific surface area and rich pore structure. The lithium-ion batteries prepared using the carbon materials of Examples 1-5 have a larger reversible specific capacity and better cycle stability.

[0097] As can be seen from Examples 1, 2, and 3, using an activator alone or a pore expander alone is not conducive to increasing the specific surface area of ​​carbon materials or improving the stability of lithium-ion batteries.

[0098] As can be seen from Examples 1, 4, and 5, excessive amounts of activator or pore expander are detrimental to pore development.

[0099] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0100] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0101] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a carbon anode material derived from biomass waste wood chips, characterized in that, Includes the following steps: (1) The sawdust was crushed, sieved, washed and dried, and then pre-carbonized to obtain a pre-carbonized sample; (2) After mixing the pre-carbonized sample with the activator, deionized water is added and stirred to dissolve the activator. Then, the mixture is heated and dried to remove moisture to obtain the mixture. (3) The mixture is ground and mixed with a pore-expanding agent and then calcined to obtain an activated sample; (4) The activated sample is washed, dried and then ground to obtain porous carbon material.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the pre-carbonized sample to the activator is 1:(2~4).

3. The preparation method according to claim 1, characterized in that, The mass ratio of the mixture to the pore-expanding agent is 1:(0.1~0.3).

4. The preparation method according to claim 1, characterized in that, The activator includes one or more of KOH, KHCO3, KMnO4, K2CO3, and H3PO4; The pore-expanding agent includes one or more of urea, thiourea, diammonium hydrogen phosphate, and ammonium sulfate.

5. The preparation method according to claim 1, characterized in that, In step (1), the wood chips are crushed and then passed through a 40-70 mesh sieve; And / or, the drying temperature in step (1) is 80~100℃ and the time is 6~12h; And / or, the pre-carbonization treatment in step (1) is heating at 200~400℃ for 1~3h under an inert gas.

6. The preparation method according to claim 1, characterized in that, The drying temperature in step (2) is 100~120℃ and the time is 2~4h; And / or, in step (3), calcination is performed by heating at 600~900℃ for 1~4h under an inert gas. And / or, in step (4), the drying temperature is 60~100℃ and the drying time is 24~36h.

7. The preparation method according to claim 1, characterized in that, The specific surface area of ​​the porous carbon material is 1700 m². 2 / g or more; And / or, the particle size of the porous carbon material is 0.1~10 nm.

8. A negative electrode material, characterized in that, Prepared by the method described in any one of claims 1 to 7.

9. A lithium-ion battery, characterized in that, It includes a negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector, the negative electrode active material including the negative electrode material according to claim 8.

10. An electrical device, characterized in that, Including the lithium-ion battery as described in claim 9.

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