WO2024077665A1 - 一种锂硫电池正极材料的制备方法、正极材料及应用 - Google Patents

一种锂硫电池正极材料的制备方法、正极材料及应用 Download PDF

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WO2024077665A1
WO2024077665A1 PCT/CN2022/127600 CN2022127600W WO2024077665A1 WO 2024077665 A1 WO2024077665 A1 WO 2024077665A1 CN 2022127600 W CN2022127600 W CN 2022127600W WO 2024077665 A1 WO2024077665 A1 WO 2024077665A1
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lithium
positive electrode
electrode material
sulfur battery
sulfur
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PCT/CN2022/127600
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English (en)
French (fr)
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葛震
赖浩然
陈曦
李际洋
吴孟强
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电子科技大学长三角研究院(湖州)
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Publication of WO2024077665A1 publication Critical patent/WO2024077665A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/30—Active carbon
    • C01B32/312—Preparation
    • C01B32/318—Preparation characterised by the starting materials
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/30—Active carbon
    • C01B32/312—Preparation
    • C01B32/336—Preparation characterised by gaseous activating agents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention belongs to the technical field of electrode material preparation, and in particular relates to a preparation method of a lithium-sulfur battery positive electrode material, a positive electrode material and an application thereof.
  • lithium-ion batteries are one of the most widely used energy storage systems, but traditional cathode materials can no longer meet the requirements of current equipment for high capacity and high energy density of batteries.
  • the theoretical capacity of sulfur is 1675mAh g -1 , which is much higher than the existing cathode materials.
  • the theoretical energy density of the battery assembled with lithium metal can reach 2600Wh kg -1 .
  • the insulating properties of sulfur, the volume expansion during discharge, and the shuttle effect of lithium polysulfide generated during the charge and discharge process seriously affect the performance of lithium-sulfur batteries.
  • porous carbon materials are currently widely used as carrier materials for sulfur, including graphene, carbon nanotubes, mesoporous carbon, biomass pyrolysis carbon, etc.
  • Carbon materials themselves have good electrical conductivity, can provide a conductive network, and improve the electrochemical reaction activity of sulfur; on the other hand, the rich pore structure can buffer the volume expansion during discharge and maintain the structural stability of the electrode.
  • Existing porous carbon is mostly powder material.
  • the production of lithium-sulfur battery electrodes is by mixing sulfur, porous carbon, conductive carbon, and a binder, preparing a slurry and then scraping it onto the current collector. Due to the insulating properties of sulfur, it is difficult to form an effective conductive network, and the binder will produce invalid sites, reducing the performance of the lithium-sulfur battery.
  • Wood is cheap, renewable, has a regular pore structure and good mechanical strength, and can maintain a complete three-dimensional conductive network through carbonization, making it an ideal sulfur carrier material.
  • direct carbonization will result in poor mechanical strength of the prepared porous carbon skeleton, or even direct pulverization, and the density and pore structure of the carbon skeleton are limited by the properties of the raw materials and are difficult to adjust.
  • the existing lithium-sulfur battery preparation method uses mixed sulfur, porous carbon, and conductive carbon, which is difficult to form an effective conductive network and requires additional addition of binders, resulting in poor performance of the lithium-sulfur battery;
  • the porous carbon skeleton obtained by direct carbonization of wood has poor mechanical strength and may even be directly pulverized.
  • the density and pore structure of the carbon skeleton are limited by the properties of the raw materials and are difficult to adjust.
  • the present invention provides a method for preparing a positive electrode material for a lithium-sulfur battery.
  • the present invention is achieved by providing a method for preparing a positive electrode material for a lithium-sulfur battery, the method comprising:
  • the natural wood is subjected to delignification, pre-compression, high-temperature carbonization and activation pore-forming treatment to obtain a self-supporting porous carbon skeleton material with a hierarchical pore structure of both micropores and nanopores;
  • Sulfur is loaded on a self-supporting porous carbon skeleton material having a hierarchical pore structure of both micropores and nanopores by a solid phase method or a liquid phase method to obtain the lithium-sulfur battery positive electrode material.
  • the preparation method of the lithium-sulfur battery positive electrode material comprises the following steps:
  • Step 1 Cut the natural wood to obtain wood slices; immerse the obtained wood slices in a chemical washing solution for removing lignin and hemicellulose.
  • the removal of lignin and hemicellulose can obtain a richer pore structure, while reducing the density and hardness of the natural wood, thereby achieving the purpose of softening the wood;
  • Step 2 repeatedly soaking and washing the impregnated wood slices with clean water to remove alkaline components in the washing liquid, and then drying or freeze-drying the wood slices;
  • Step 3 Pre-compressing the dried wood slices using a press can further improve the density and compressive strength of the material, while achieving precise control of the density and pore structure.
  • the pre-compressed wood slices are subjected to high-temperature annealing to obtain a self-supporting porous carbon skeleton material.
  • Step 4 activating the obtained self-supporting porous carbon skeleton material, obtaining a richer nanopore structure through high-temperature etching with gas, and obtaining a porous carbon material with a hierarchical pore structure of both micropores and nanopores;
  • Step five loading sulfur on the obtained porous carbon material with a hierarchical pore structure by a solid phase method or a liquid phase method to obtain the lithium-sulfur battery positive electrode material.
  • the natural wood is any one of fir, birch, balsa, basswood, beech, pine, poplar, oak, willow, elm, maple, holly, walnut, teak and ebony;
  • the thickness of the wood slice is 0.5-80 mm.
  • the chemical washing liquid for removing lignin and hemicellulose is composed of one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, ammonium carbonate, sodium sulfite, potassium sulfite, and ammonium sulfite;
  • the concentration of the chemical washing solution used for removing lignin and hemicellulose is 0.5-10 mol/L;
  • the immersion time is 1-24 hours, and the immersion temperature is 20-100°C.
  • step 2 the drying temperature is 40-80° C., and the drying time is 6-48 hours; in step 3, the pre-compression pressure is 1-200 MPa, and the pressure holding time is 0.1-12 hours; the thickness of the wood slice after pre-compression is 3%-80% of the thickness of the wood slice before compression;
  • the high temperature annealing treatment includes: performing a high temperature carbonization treatment in an inert atmosphere;
  • the inert atmosphere is nitrogen or argon; the temperature of the high-temperature carbonization is 500-1500° C., and the carbonization time is 1-12 hours.
  • the step of activating the obtained self-supporting biomass porous carbon to obtain a porous carbon material having a hierarchical pore structure comprises:
  • the obtained self-supporting biomass porous carbon is placed in an activation atmosphere for heating treatment to obtain a porous carbon material having a hierarchical pore structure of micropores and nanopores;
  • the activation atmosphere is composed of one or more of water vapor, flue gas, carbon dioxide and air; the activation heating temperature is 600-1000° C., and the activation heating time is 1-12 hours.
  • the method of loading sulfur on the porous carbon material having a hierarchical pore structure by a solid phase method or a liquid phase method comprises:
  • the method of loading sulfur on the porous carbon material with a hierarchical pore structure by a solid phase method includes: evenly sprinkling sulfur powder on the surface of the porous carbon material with a hierarchical pore structure, and then heating at 140-170° C. for 0.5-12 h to melt the sulfur powder, thereby obtaining the lithium-sulfur battery positive electrode material.
  • the method of loading sulfur on the porous carbon material with a hierarchical pore structure by a liquid phase method comprises: dropping a sulfur carbon disulfide solution on the surface of the porous carbon material with a hierarchical pore structure, and heating the material at 140-170° C. for 0.5-12 h after the solvent evaporates, thereby obtaining the lithium-sulfur battery positive electrode material.
  • Another object of the present invention is to provide a lithium-sulfur battery positive electrode material prepared using the method for preparing the lithium-sulfur battery positive electrode material.
  • Another object of the present invention is to provide a lithium-sulfur battery, wherein the lithium-sulfur battery is assembled from the lithium-sulfur battery positive electrode material and a metallic lithium negative electrode.
  • the lithium-sulfur battery is a button cell or a square cell.
  • the present invention uses delignification, pre-compression, high-temperature carbonization and activation pore formation to adjust the density and pore structure of the wood-derived porous carbon skeleton.
  • activation pore formation nanopores can be introduced on the micron-level pipeline wall, inhibiting the dissolution and shuttling of lithium polysulfide and improving the cycle stability of the battery.
  • the pre-compression treatment can effectively control the density of the carbon skeleton, improve the strength, and improve the conductivity of the three-dimensional current collector while maintaining the pore structure, which is more conducive to the conduction of electrons.
  • the self-supporting porous carbon material of the present invention has a hierarchical pore structure and can be used to prepare lithium-sulfur batteries. It can effectively inhibit the dissolution and diffusion of lithium polysulfide and greatly improve the cycle stability and rate performance of the battery. Pre-compression treatment can increase the density and compressive strength of the porous carbon skeleton and avoid crushing and pulverization during battery assembly.
  • the self-supporting carbon skeleton itself forms a three-dimensional conductive network, which can ensure the effective transmission of electrons and ions in the battery system, avoid the use of traditional conductive additives, binders and current collectors, and greatly save costs.
  • the technical solution of the present invention fills the technical gap in the industry at home and abroad: the present invention proposes for the first time a method for preparing a self-supporting porous carbon skeleton with controllable density, and applies it to the field of lithium-sulfur batteries.
  • the density and pore structure of the currently reported biomass carbon materials are limited by the original materials and are difficult to adjust effectively.
  • the preparation process of delignification, pre-compression, high-temperature carbonization and activation treatment proposed in the present invention can achieve precise control of the density and pore structure of the prepared carbon skeleton material, filling the technical gap in the relevant field.
  • the design of self-supporting porous carbon with hierarchical pore structure can effectively improve the cycle stability and rate performance of lithium-sulfur batteries.
  • FIG1 is a flow chart of a method for preparing a positive electrode material for a lithium-sulfur battery provided in an embodiment of the present invention
  • FIG2 is a cross-sectional scanning electron microscope image of a self-supporting porous carbon skeleton provided in an embodiment of the present invention
  • FIG3 is a cycle performance diagram of a lithium-sulfur battery composite positive electrode material provided by an embodiment of the present invention.
  • FIG. 4 is a rate performance diagram of a lithium-sulfur battery composite positive electrode material provided in an embodiment of the present invention.
  • the natural wood provided in the embodiment of the present invention can be selected from fir, birch, balsa, basswood, beech, pine, poplar, oak, willow, elm, maple, holly, walnut, teak, ebony and other woods.
  • the thickness of the natural wood slices provided by the embodiment of the present invention ranges from 0.5 to 80 mm.
  • the washing liquid for removing lignin and hemicellulose provided in the embodiment of the present invention is composed of one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, ammonium carbonate, sodium sulfite, potassium sulfite and ammonium sulfite.
  • the concentration of the prepared washing solution provided in the embodiment of the present invention is in the range of 0.5-10 mol/L.
  • the embodiment of the present invention provides that the wood chips are immersed in the washing liquid, the immersion time is 1-24 hours, and the temperature is controlled at 20-100°C.
  • the washed wood chips or bamboo chips provided in the embodiment of the present invention are repeatedly soaked and washed with clean water to wash away the residual eluent, and then dried or freeze-dried to remove moisture, with the drying temperature being 40-80° C. and the drying time being 6-48 h.
  • the treated wood chips provided in the embodiment of the present invention are pre-compressed using a press, the pressure range is 1-200 MPa, and the pressure holding time is 0.1-12 h.
  • the pre-compression treatment of the wood chips by the present invention can effectively control the density of the carbon skeleton, improve the strength, and improve the conductivity of the three-dimensional current collector while maintaining the pore structure, which is more conducive to the conduction of electrons.
  • the thickness of the compressed wood chips provided by the embodiment of the present invention is 3%-80% of the thickness before compression.
  • the embodiment of the present invention provides a method for high-temperature carbonization of compressed wood chips in an inert atmosphere, wherein the carbonization temperature is 500-1500° C. and the carbonization time is 1-12 h.
  • the inert atmosphere refers to nitrogen or argon.
  • the activation treatment provided in the embodiment of the present invention refers to placing the porous carbon skeleton obtained after carbonization in an activation atmosphere for heating treatment, the activation atmosphere is composed of one or more of water vapor, flue gas, carbon dioxide, and air, the activation heating temperature is 600-1000 ° C, and the activation heating time is 1-12 h.
  • the embodiment of the present invention can introduce nanopores on the micron-scale pipeline wall through activation pore formation, inhibit the dissolution and shuttling of lithium polysulfide, and improve the cycle stability of the battery.
  • the self-supporting carbon skeleton material prepared in the embodiment of the present invention has a specific surface area range of 100-3000 m2 /g, a density range of 0.02-1.80 g/ cm3 , and has a hierarchical pore structure of micropores and nanopores.
  • the self-supporting carbon skeleton provided in the embodiment of the present invention is a three-dimensional conductive network itself, which can avoid the use of traditional conductive additives, binders and current collectors, and can greatly save costs.
  • the loading of sulfur on porous carbon uses a solid phase method to evenly sprinkle sulfur powder on the surface of the porous carbon skeleton, and then heat it to melt the sulfur and fully contact the carbon skeleton, the heating temperature is 140-170 ° C, and the heating time is 0.5-12 h.
  • the use of a liquid phase method refers to dropping a sulfur carbon disulfide solution on the surface of the porous carbon skeleton, and then heating it after the solvent evaporates, the heating temperature is 140-170 ° C, and the heating time is 0.5-12 h.
  • the mass proportion of sulfur in the composite positive electrode material provided by the embodiment of the present invention is 30-90%.
  • the self-supporting lithium-sulfur battery composite positive electrode material and the metal lithium negative electrode assembled battery provided by the embodiment of the present invention do not need to add additional conductive additives, binders and current collectors, and are suitable for button batteries and square batteries.
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • the balsa wood was cut into 0.8 mm thick chips, which were immersed in an eluent (2.5 mol/L NaOH + 0.5 mol/L Na 2 SO 3 aqueous solution), heated at 80 ° C for 12 h, and then repeatedly washed with distilled water to remove the adsorbed alkali solution, and freeze-dried to remove water.
  • the treated chips were pre-compressed using a press with a pressure of 16 MPa and a holding time of 2 h. High-temperature carbonization treatment was then performed under an argon atmosphere at a carbonization temperature of 1000 ° C for 2 h, and finally activation treatment was performed.
  • the carbonized material was heated at 750 ° C for 1 h in a carbon dioxide atmosphere for activation and pore formation to obtain a self-supporting carbon skeleton material.
  • a CS 2 solution of S was added dropwise and heated at 155 ° C for 1 h to obtain a composite positive electrode material.
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • Cut basswood into 0.8mm thick wood chips immerse the wood chips in the eluent (2.5mol/LKOH+0.5mol/LNa 2 SO 3 aqueous solution), heat at 100°C for 6h, then wash the wood chips repeatedly with distilled water, and freeze-dry to remove water.
  • perform high-temperature carbonization treatment under an argon atmosphere, at a carbonization temperature of 1000°C and a carbonization time of 2h, and finally perform activation treatment, heating the carbonized material at 600°C for 1h in a water vapor atmosphere for activation and pore formation to obtain a self-supporting carbon skeleton material.
  • Embodiment 3 is a diagrammatic representation of Embodiment 3
  • the carbonized material is heated at 700°C for 2h in a carbon dioxide atmosphere for activation and pore formation to obtain a self-supporting carbon skeleton material.
  • the lithium-sulfur battery assembled based on the self-supporting porous carbon skeleton material proposed in the present invention exhibits a specific capacity of 1120mAh g -1 and good cycle stability at a charge and discharge rate of 0.1C. As shown in Figure 3, after 100 charge and discharge cycles, the specific capacity of the device can still be maintained at 674mAh g -1 .
  • the higher capacity and good cycle stability are mainly attributed to the construction of the hierarchical pore structure. The introduction of a large number of nanopores plays a positive role in improving the stability of the battery.
  • the lithium-sulfur battery based on the self-supporting porous carbon skeleton material proposed in the present invention has excellent rate performance, which is mainly attributed to the construction of the three-dimensional conductive network, which is conducive to the rapid conduction of electrons, and the structure of the micropores is also conducive to the diffusion of the electrolyte, thereby achieving good rate performance.
  • the design of the self-supporting carbon skeleton can form an efficient conductive path, replace the conductive additives, current collectors and binders in the traditional electrode preparation method, simplify the production process, and effectively reduce the cost of battery preparation.

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Abstract

本发明属于电极材料制备技术领域，公开了一种锂硫电池正极材料的制备方法、正极材料及应用，包括：对木材进行脱木质素、预压缩和活化造孔处理得到具有微米孔和纳米孔的分级孔结构的自支撑碳骨架材料；利用固相法或者液相法在具有微米孔和纳米孔的分级孔结构的自支撑碳骨架材料上进行硫的负载，得到所述锂硫电池正极材料。本发明利用脱木质素，预压缩和活化造孔的方法调节木材衍生的多孔碳骨架的密度和孔结构。通过活化造孔在微米级的管道壁上引入纳米孔，抑制多硫化锂的溶解和穿梭，改善电池的循环稳定性；预压缩处理有效控制碳骨架的密度，提高强度，在保持孔结构的条件下，提高三维集流体的电导率，更有利于电子的传导。

Description

一种锂硫电池正极材料的制备方法、正极材料及应用 技术领域
本发明属于电极材料制备技术领域，尤其涉及一种锂硫电池正极材料的制备方法、正极材料及应用。
 背景技术
目前，锂离子电池是应用最为广泛的储能体系之一，但是传统的正极材料已经满足不了现在的设备对电池高容量，高能量密度的要求。硫的理论容量达1675mAh g -1，远高于现有的正极材料，与金属锂组装电池的理论能量密度可达到2600Wh kg -1。不过硫的绝缘性质，放电过程中的体积膨胀，以及充放电过程产生的多硫化锂的穿梭效应严重影响了锂硫电池性能的发挥。
为了解决上述问题，目前普遍使用多孔碳材料作为硫的载体材料，包括石墨烯，碳纳米管，介孔碳，生物质热解碳等。碳材料本身具有良好的导电性，可以提供导电网络，提高硫的电化学反应活性；另一方面，丰富的孔洞结构可以缓冲放电过程中的体积膨胀，保持电极的结构稳定性。现有的多孔碳多为粉末材料，锂硫电池电极制作是通过混合硫，多孔碳，导电碳，粘结剂的方式，调制成浆料再刮涂到集流体上，由于硫的绝缘性质，这样很难形成有效的导电网络，而且粘结剂会产生无效位点，降低锂硫电池的性能。
木材具有价格低廉，可再生的优势，且具有规整的孔道结构和良好的机械强度，通过碳化处理能够保持完整的三维导电网络，是理想的硫的载体材料。但是，直接碳化会导致制备的多孔碳骨架力学强度差，甚至直接粉化，而且碳骨架的密度和孔结构受限于原材料的性质，难以调节。
 技术问题
通过上述分析，现有技术存在的问题及缺陷为：
（1）现有的锂硫电池制备方法利用混合硫，多孔碳，导电碳，很难形成有效的导电网络，需要额外添加粘结剂等，得到的锂硫电池性能不佳；
（2）木材直接碳化处理得到的多孔碳骨架力学强度差，甚至直接粉化，而且碳骨架的密度和孔结构受限于原材料的性质，难以调节。
 技术解决方案
针对现有技术存在的问题，本发明提供了一种锂硫电池正极材料的制备方法。
本发明是这样实现的，一种锂硫电池正极材料的制备方法，所述锂硫电池正极材料的制备方法包括：
对天然木材进行脱木质素、预压缩、高温碳化和活化造孔处理得到兼具微米孔和纳米孔的分级孔结构的自支撑多孔碳骨架材料；
利用固相法或者液相法在兼具微米孔和纳米孔的分级孔结构的自支撑多孔碳骨架材料上进行硫的负载，得到所述锂硫电池正极材料。
进一步，所述锂硫电池正极材料的制备方法包括以下步骤：
步骤一，将天然木材进行切割得到木材薄片；将得到的木材薄片浸渍于用于脱除木质素和半纤维素的化学洗液中，木质素和半纤维素的脱除可以获得更丰富的孔结构，同时降低天然木材的密度和硬度，达到软化木质的目的；
步骤二，将浸渍后的木材薄片利用清水反复浸泡、清洗，除去洗液中的碱性成分，再对所述木材薄片进行烘干或冷冻干燥处理；
步骤三，利用压力机对干燥后的木材薄片进行预压缩处理，可以进一步地提高材料的密度和抗压缩强度，同时实现对密度和孔结构的精准调控，将预压缩处理后的木材薄片进行高温退火处理，得到自支撑多孔碳骨架材料；
步骤四，将得到的自支撑多孔碳骨架材料进行活化处理，通过气体的高温刻蚀得到更丰富的纳米孔结构，得到兼具微米孔和纳米孔的分级孔结构的多孔碳材料；
步骤五，利用固相法或者液相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载，得到所述锂硫电池正极材料。
进一步，所述天然木材为杉木，桦木，巴沙木，椴木，榉木，松木，杨木，橡木，柳木，榆木，枫木，冬青木，核桃木，柚木，乌木中的任意一种；
所述木材薄片的厚度为0.5-80mm。
进一步，所述用于脱除木质素和半纤维素的化学洗液由氢氧化钠、碳酸钠、氢氧化钾、碳酸钾、碳酸铵、亚硫酸钠、亚硫酸钾、亚硫酸铵的一种或多种组成；
所述用于脱除木质素和半纤维素的化学洗液的浓度为0.5-10mol/L；
所述浸渍时间为1-24h，浸渍温度为20-100℃。
进一步，所述步骤二中烘干温度为40-80℃，烘干时间为6-48h；所述步骤三中预压缩的压力为1-200MPa，保压时间为0.1-12h；预压缩后的木材薄片厚度为压缩前木材薄片厚度的3%-80%；
所述高温退火处理包括：在惰性气氛下进行高温碳化处理；
所述惰性气氛为氮气或者氩气；所述高温碳化的温度为500-1500℃，碳化时间为1-12h。
进一步，所述将得到的自支撑生物质多孔碳进行活化处理，得到具有分级孔结构的多孔碳材料包括：
将得到的自支撑生物质多孔碳置于活化气氛中进行加热处理，得到具有微米孔和纳米孔的分级孔结构的多孔碳材料；
所述活化气氛由水蒸气，烟道气，二氧化碳，空气的一种或多种组成；所述活化加热温度为600-1000℃，活化加热时间为1-12h。
进一步，所述利用固相法或者液相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载包括：
利用固相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载包括：将硫粉均匀洒在具有分级孔结构的多孔碳材料表面，再在140-170℃下加热0.5-12h融化硫粉，得到所述锂硫电池正极材料
利用液相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载包括：将硫的二硫化碳溶液滴在具有分级孔结构的多孔碳材料表面，并于溶剂挥发后于140-170℃下加热0.5-12h，得到所述锂硫电池正极材料。
本发明的另一目的在于提供一种利用所述锂硫电池正极材料的制备方法制备的锂硫电池正极材料。
本发明的另一目的在于提供一种锂硫电池，所述锂硫电池由所述锂硫电池正极材料与金属锂负极组装得到。
进一步，所述锂硫电池为扣式电池或方形电池。
 有益效果
本发明利用脱木质素，预压缩，高温碳化和活化造孔的方法调节木材衍生的多孔碳骨架的密度和孔结构。通过活化造孔可以在微米级的管道壁上引入纳米孔，抑制多硫化锂的溶解和穿梭，改善电池的循环稳定性。预压缩处理可以有效控制碳骨架的密度，提高强度，在保持孔结构的条件下，提高三维集流体的电导率，更有利于电子的传导。
本发明的自支撑多孔碳材料具有分级孔结构特征，可以用于制备锂硫电池，可以有效地抑制多硫化锂的溶解和扩散，大幅提高电池的循环稳定性和倍率性能。预压缩处理可以提高多孔碳骨架的密度和抗压缩强度，避免在电池组装过程中发生破碎和粉化。此外，自支撑碳骨架本身形成三维导电网络，能够保证电池体系内电子和离子的有效传输，可以避免传统的导电添加剂，粘结剂和集流体的使用，可以大幅节约成本。
本发明的技术方案填补了国内外业内技术空白：本发明首次提出了密度可控的自支撑多孔碳骨架的制备方法，并应用于锂硫电池领域。目前所报道的生物质炭材料的密度和孔结构受限于原始材料，很难进行有效调节。本发明提出的脱木质素，预压缩，高温碳化和活化处理的制备工艺可以实现对制得的碳骨架材料的密度和孔结构的精准调控，填补了相关领域的技术空白。分级孔结构自支撑多孔碳的设计能够有效提高锂硫电池的循环稳定性和倍率性能。
 附图说明
图1是本发明实施例提供的锂硫电池正极材料的制备方法流程图；
图2是本发明实施例提供的自支撑多孔碳骨架的截面扫描电镜图；
图3是本发明实施例提供的锂硫电池复合正极材料的循环性能图；
图4是本发明实施例提供的锂硫电池复合正极材料的倍率性能图。
 本发明的实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
为了使本领域技术人员充分了解本发明如何具体实现，该部分是对权利要求技术方案进行展开说明的解释说明实施例。
如图1所示，本发明实施例提供的锂硫电池正极材料的制备方法包括：
S101，将天然木材进行切割得到木材薄片；将得到的木材薄片浸渍于用于脱除木质素和半纤维素的化学洗液中；
S102，将浸渍后的木材薄片利用清水反复浸泡、清洗，再对所述木材薄片进行烘干或冷冻干燥处理；
S103，利用压力机对干燥后的木材薄片进行预压缩处理，将预压缩处理后的木材薄片进行高温退火处理，得到自支撑生物质多孔碳；
S104，将得到的自支撑生物质多孔碳进行活化处理，得到具有分级孔结构的多孔碳材料；
S105，利用固相法或者液相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载，得到所述锂硫电池正极材料。
本发明实施例提供的天然木材可选自于杉木，桦木，巴沙木，椴木，榉木，松木，杨木，橡木，柳木，榆木，枫木，冬青木，核桃木，柚木，乌木等木材。
本发明实施例提供的天然木材切片的厚度范围在0.5-80 mm。
本发明实施例提供的脱除木质素和半纤维素的洗液由氢氧化钠，碳酸钠，氢氧化钾，碳酸钾，碳酸铵，亚硫酸钠，亚硫酸钾，亚硫酸铵的一种或多种组成。
本发明实施例提供的配制的洗液浓度范围在0.5-10 mol/L。
本发明实施例提供的将木片浸渍于洗液之中，浸渍时间在1-24 h，温度控制在20-100 ℃。
本发明实施例提供的洗脱之后的木片或竹片要经过清水反复的浸泡和清洗，洗净残余的洗脱液，再经过烘干或者冷冻干燥除去水分，烘干温度在40-80 ℃，烘干时间6-48 h。
本发明实施例提供的处理后的木片使用压力机进行预压缩，压力范围在1-200 MPa，保压时间0.1-12 h。本发明对木片进行预压缩处理可以有效控制碳骨架的密度，提高强度，在保持孔结构的条件下，提高三维集流体的电导率，更有利于电子的传导。
本发明实施例提供的压缩后的木片的厚度为压缩前的厚度的3%-80%。
本发明实施例提供的将压缩后的木片在惰性气氛下进行高温碳化，碳化温度500-1500 ℃，碳化时间1-12 h，惰性气氛指氮气或者氩气。
本发明实施例提供的活化处理指将碳化后得到的多孔碳骨架置于活化气氛中加热处理，活化气氛由水蒸气，烟道气，二氧化碳，空气的一种或多种组成，活化加热温度600-1000 ℃，活化加热时间1-12 h。本发明实施例通过活化造孔可以在微米级的管道壁上引入纳米孔，抑制多硫化锂的溶解和穿梭，改善电池的循环稳定性。
本发明实施例提供的制备得到的自支撑碳骨架材料的比表面积范围在100-3000 m 2/g，密度范围在0.02-1.80 g/cm 3，同时具有微米孔和纳米孔的分级孔结构。本发明实施例提供的自支撑碳骨架本身就是三维导电网络，可以避免传统的导电添加剂，粘结剂和集流体的使用，可以大幅节约成本。
本发明实施例提供的在多孔碳上进行硫的负载，使用固相法指将硫粉均匀洒在多孔碳骨架表面，再进行加热处理使硫融化，与碳骨架充分接触，加热温度140-170 ℃，加热时间0.5-12 h。使用液相法指将硫的二硫化碳溶液滴在多孔碳骨架表面，待溶剂挥发后，再进行加热处理，加热温度140-170 ℃，加热时间0.5-12 h。
本发明实施例提供的复合正极材料中硫的质量比例在30-90%。
本发明实施例提供的自支撑锂硫电池复合正极材料与金属锂负极组装电池，无需额外加入导电添加剂，粘结剂和集流体，适用于扣式电池和方形电池。
为了证明本发明的技术方案的创造性和技术价值，该部分是对权利要求技术方案进行具体产品上或相关技术上的应用实施例。
下面结合具体实施例对本发明的技术方案作进一步说明。
实施例1：
将巴沙木切割成0.8mm厚的木片，将木片浸渍于洗脱液之中（2.5mol/LNaOH+0.5mol/LNa 2SO 3水溶液），加热80℃12h，之后使用蒸馏水反复清洗木片，除去吸附的碱液，进行冷冻干燥除水。使用压力机将处理后的木片进行预压缩，压强16MPa，保压时间2h。再进行高温碳化处理，在氩气气氛下，碳化温度1000℃，碳化时间2h，最后进行活化处理，将碳化后的材料在二氧化碳气氛中加热750℃1h进行活化造孔，得到自支撑碳骨架材料。滴加S的CS 2溶液，155℃加热1h，得到复合正极材料。
实施例2：
将椴木切割成0.8mm厚的木片，将木片浸渍于洗脱液之中（2.5mol/LKOH+0.5mol/LNa 2SO 3水溶液）,加热100℃6h，之后使用蒸馏水反复清洗木片，进行冷冻干燥除水。使用压力机将处理后的木片进行预压缩，压强30MPa，保压时间2h。再进行高温碳化处理，在氩气气氛下，碳化温度1000℃，碳化时间2h，最后进行活化处理，将碳化后的材料在水蒸气气氛中加热600℃1h进行活化造孔，得到自支撑碳骨架材料。滴加S的CS 2溶液，155℃加热1h，得到复合正极材料。
实施例3：
将橡木切割成2mm厚的木片，将木片浸渍于洗脱液之中（2mol/LNaOH+1mol/LNa 2SO 3水溶液）,加热80℃6h，之后使用蒸馏水反复清洗木片，80℃12h常压烘干除水。使用压力机将处理后的木片进行预压缩，压强25MPa，保压时间1h。再进行高温碳化处理，在氮气气氛下，碳化温度1000℃，碳化时间2h，最后进行活化处理，将碳化后的材料在二氧化碳气氛中加热700℃2h进行活化造孔，得到自支撑碳骨架材料。在碳骨架表面均匀撒上硫粉，160℃加热2h，得到复合正极材料。
本发明实施例在研发或者使用过程中取得了一些积极效果，和现有技术相比的确具备很大的优势，下面内容结合试验过程的数据、图表等进行描述。
基于本发明提出的自支撑多孔碳骨架材料组装的锂硫电池在0.1C充放电倍率下表现出了1120mAh g -1的比容量和较好的循环稳定性，如图3所示，经过100次的充放电循环，器件的比容量仍能保持在674mAh g -1。较高的容量和良好的循环稳定性主要归因于分级孔结构的构筑，大量的纳米孔的引入对提升电池的稳定性起到了积极作用。在倍率性能方面，如图4所示，随着电流密度的增加，组装的锂硫电池在0.1C，0.2C,0.5C,1C和2C的倍率下，放电比容量分别达到1132,853,706,633,499mAh g -1，随后电流密度回到了0.1C，比容量也能回复到829 mAh g -1，这些结果表明基于本发明提出的自支撑多孔碳骨架材料的锂硫电池具有优异的倍率性能，主要归因于三维导电网络的构筑有利于电子的快速传导，微米孔的结构也有利于电解液的扩散，从而实现良好的倍率性能。此外，自支撑碳骨架的设计可以形成高效的导电通路，取代传统电极制备方法中的导电添加剂，集流体和粘结剂，简化生产工艺，有效降低电池制备成本。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，都应涵盖在本发明的保护范围之内。

Claims (10)

  1. 一种锂硫电池正极材料的制备方法，其特征在于，所述锂硫电池正极材料的制备方法包括：
    对木材进行脱木质素、预压缩和活化造孔处理得到具有微米孔和纳米孔的分级孔结构的自支撑碳骨架材料；
    利用固相法或者液相法在具有微米孔和纳米孔的分级孔结构的自支撑碳骨架材料上进行硫的负载，得到所述锂硫电池正极材料。
  2. 如权利要求1所述锂硫电池正极材料的制备方法，其特征在于，所述锂硫电池正极材料的制备方法包括以下步骤：
    步骤一，将天然木材进行切割得到木材薄片；将得到的木材薄片浸渍于用于脱除木质素和半纤维素的化学洗液中；
    步骤二，将浸渍后的木材薄片利用清水反复浸泡、清洗，再对所述木材薄片进行烘干或冷冻干燥处理；
    步骤三，利用压力机对干燥后的木材薄片进行预压缩处理，将预压缩处理后的木材薄片进行高温退火处理，得到自支撑生物质多孔碳；
    步骤四，将得到的自支撑生物质多孔碳进行活化处理，得到具有分级孔结构的多孔碳材料；
    步骤五，利用固相法或者液相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载，得到所述锂硫电池正极材料。
  3. 如权利要求2所述锂硫电池正极材料的制备方法，其特征在于，所述天然木材为杉木，桦木，巴沙木，椴木，榉木，松木，杨木，橡木，柳木，榆木，枫木，冬青木，核桃木，柚木，乌木中的任意一种；
    所述木材薄片的厚度为0.5-80mm。
  4. 如权利要求2所述锂硫电池正极材料的制备方法，其特征在于，所述用于脱除木质素和半纤维素的化学洗液由氢氧化钠、碳酸钠、氢氧化钾、碳酸钾、碳酸铵、亚硫酸钠、亚硫酸钾、亚硫酸铵的一种或多种组成；
    所述用于脱除木质素和半纤维素的化学洗液的浓度为0.5-10mol/L；
    所述浸渍时间为1-24h，浸渍温度为20-100℃。
  5. 如权利要求2所述锂硫电池正极材料的制备方法，其特征在于，所述步骤二中烘干温度为40-80℃，烘干时间为6-48h；所述步骤三中预压缩的压力为1-200MPa，保压时间为0.1-12h；预压缩后的木材薄片厚度为压缩前木材薄片厚度的3%-80%；
    所述高温退火处理包括：在惰性气氛下进行高温碳化处理；
    所述惰性气氛为氮气或者氩气；所述高温碳化的温度为500-1500℃，碳化时间为1-12h。
  6. 如权利要求2所述锂硫电池正极材料的制备方法，其特征在于，所述将得到的自支撑生物质多孔碳进行活化处理，得到具有分级孔结构的多孔碳材料包括：
    将得到的自支撑生物质多孔碳置于活化气氛中进行加热处理，得到具有微米孔和纳米孔的分级孔结构的多孔碳材料；
    所述活化气氛由水蒸气，烟道气，二氧化碳，空气的一种或多种组成；所述活化加热温度为600-1000℃，活化加热时间为1-12h。
  7. 如权利要求2所述锂硫电池正极材料的制备方法，其特征在于，所述利用固相法或者液相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载包括：
    利用固相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载包括：将硫粉均匀洒在具有分级孔结构的多孔碳材料表面，再在140-170℃下加热0.5-12h融化硫粉，得到所述锂硫电池正极材料
    利用液相法在得到的具有分级孔结构的多孔碳材料上进行硫的负载包括：将硫的二硫化碳溶液滴在具有分级孔结构的多孔碳材料表面，并于溶剂挥发后于140-170℃下加热0.5-12h，得到所述锂硫电池正极材料。
  8. 一种利用如权利要求1-7任意一项所述锂硫电池正极材料的制备方法制备的锂硫电池正极材料。
  9. 一种锂硫电池，其特征在于，所述锂硫电池由权利要求8所述锂硫电池正极材料与金属锂负极组装得到。
  10. 如权利要求9所述锂硫电池，其特征在于，所述锂硫电池为扣式电池或方形电池。
PCT/CN2022/127600 2022-10-14 2022-10-26 一种锂硫电池正极材料的制备方法、正极材料及应用 WO2024077665A1 (zh)

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