锂电池用鱼鳞基炭材料的制备与表征
发布时间：2018-08-21 12:59
【摘要】：近年来,电动车飞猛发展,对电池能量密度提出更高要求。由于多孔炭材料优异的理化性能,因此被广泛地应用于储能领域,特别是具有分级孔结构的炭材料优势显著,已经成为目前研究热点。本文采用废弃物鱼鳞为原料,设计制备出具有分级孔结构炭材料,并进一步将其石墨化制备了鱼鳞基石墨,目的为提高锂-硫电池正极和锂离子电池负极电化学性能。具体工作包括：第一,鱼鳞基多孔碳的制备与表征。凭借鱼鳞的组成和结构优势,以无机物为模板,有机物为碳源,制备了鱼鳞基多孔炭材料,并采用SEM、XRD、Raman、XPS等手段研究鱼鳞炭材料的碳化与活化过程。结果表明,随着碳化温度从600℃增加至900℃,炭材料的孔结构更发达。当碳化温度为900℃时,比表面高达2732 m2 g-1；ID/IG值从1.40降到1.20,石墨化度增加,缺陷度减少；同时,氮元素含量从6.54%降低到0.92%,季氮含量逐渐减少；碳化温度为900℃时,C/O摩尔比为8.49,表明炭化物还原性增加。第二,用鱼鳞基多孔炭提高锂-硫电池正极电化学性能。借助交流阻抗、循环伏安、紫外分光光谱、X射线能量色散谱分析等手段,分析不同结构的多孔炭硫正极动力学,研究鱼鳞基多孔炭硫正极的充放电反应机制,并对电解液组成与倍率及不同放电深度的关系进行表征。研究表明,当碳化温度为600-7000C,放电比容量基本维持在500-700mAh g-1。当碳化温度提升至9000C时,首次放电比容量为1612mAh g-1,经过50次循环后,容量保持率为73.6%；炭化物孔隙结构愈发达,多硫化物更易被吸附在正极表面,活性物质利用率得到提高；当碳化温度从600℃增加到900℃,电解液电阻从5.75 Ω降至1.31Ω,高电位还原峰与氧化峰位垒从0.42V降至0.22V；在充放电过程中,随着碳化温度增加,炭化物结构更完善,表面离子更少地迁移到电解液中,扩散减小,电化学可逆性增加,电极极化减小；在O.1C及1C倍率不同放电深度,紫外可见分光光谱在237nm、265nm及300nm均出现最大吸收峰,而S62-多硫离子稳定存在,鱼鳞基多孔炭硫正极吸收峰强度小于不添加的吸收峰,表明鱼鳞基多孔炭能够吸附活性物质,提高极片活性物质利用率。凭借鱼鳞基多孔炭的结构和组成优势,通过冷冻干燥法设计并制备非对称电极,对其电化学性能,充放电机制以及涂覆层厚度对非对称电极的影响进行分析研究。当非对称电极的硫含量为63%时,1C倍率下,首次放电比容量为1426 mAh g-1;经过100次循环后,比容量仍保持990 mAh g-1,库仑效率高达97%。此外,根据紫外分光光谱结果显示,放电后吸收峰强度在0.05左右,充电后吸收峰强度几乎为零,表明鱼鳞基多孔炭层将活性物质限制在硫正极一侧,阻止其溶解；非对称电极电阻(4.3 Ω)小于添加多孔炭电极电阻(7.1 Ω),表明鱼鳞基炭涂覆层作为上层集流体,为电子传导提供通道,减小界面电阻；研究涂覆层厚度对电池电化学性能的影响,选择适合涂覆层厚度,提高锂-硫电池循环性能以及能量密度。第三,鱼鳞基石墨的制备及其在锂离子电池的应用。以鱼鳞为前驱体,2800℃石墨化,制备鱼鳞基石墨。研究不同制备方法的结构变化规律,以及对锂离子负极电化学性能影响,以揭示充放电反应机制。研究表明所制备石墨材料的I2D/IG比值为1.57,比表面积为5.1 m2g-1,平均孔径为17.1 nm,(002)晶面间距0.337nm,有利于锂离子的嵌入和脱出；同时,材料低缺陷度和高石墨化度(Id/Ig=0.10)将首次库仑效率提高至73.4%；此外,采用高倍透射电镜、拉曼谱图、原子力显微镜及扫描隧道显微镜等分析手段对充放电反应机制进行初探,结果表明在一定电流密度下,锂离子不断地脱嵌将所制备石墨材料电化学剥离成2-3个碳原子层,形成具有A-B堆叠的双层石墨烯结构。
[Abstract]:In recent years, with the rapid development of electric vehicles, the energy density of batteries is required to be higher. Porous carbon materials have been widely used in the field of energy storage because of their excellent physical and chemical properties. Especially, carbon materials with hierarchical porous structure have obvious advantages and become a research hotspot. In order to improve the electrochemical performance of lithium-sulfur battery cathode and lithium-ion battery cathode, the preparation and characterization of fish-scale-based porous carbon were studied. Based on the composition and structure of fish-scale, inorganic materials were used as templates and organic materials as carbon sources. Carbonization and activation of fish-scale carbon materials were studied by means of SEM, XRD, Raman and XPS. The results show that the pore structure of the materials is more developed with the increase of the carbonization temperature from 600 C to 900 C. At the same time, the content of nitrogen decreased from 6.54% to 0.92%, and the content of quaternary nitrogen decreased gradually. The C/O molar ratio was 8.49 at the carbonization temperature of 900 C, indicating that the reducibility of carbide increased. Secondly, the electrochemical performance of lithium-sulfur battery cathode was improved by using fish-scale porous carbon. By means of energy dispersive spectroscopy, the kinetics of porous carbon-sulfur cathode with different structures was analyzed, and the charge-discharge reaction mechanism of fish-scale porous carbon-sulfur cathode was studied. When the carbonization temperature rises to 900C, the first discharge specific capacity is 1612 mAh g-1, and after 50 cycles, the capacity retention rate is 73.6%; the more developed the pore structure of carbide, the more easily the polysulfide is adsorbed on the cathode surface, and the utilization rate of active material is improved; when the carbonization temperature rises from 600 C to 900 C, the electrolyte resistance decreases from 5.75_to 1. 31_, high potential reduction peak and oxidation peak barrier decreased from 0.42 V to 0.22 V; with the increase of carbonization temperature, the structure of carbide became more perfect, the surface ions migrated less to the electrolyte, the diffusion decreased, the electrochemical reversibility increased, the electrode polarization decreased; at different discharge depths of O.1C and 1C times, the ultraviolet-visible spectroscopy spectrum was obtained. The maximum absorption peaks appeared at 237 nm, 265 nm and 300 nm, while S62-polysulfide ions existed steadily. The positive absorption peaks of fish-scale-based porous carbon and sulphur were less than those without addition. The results showed that fish-scale-based porous carbon could absorb active substances and improve the utilization rate of active substances in polar plates. The asymmetric electrode was designed and fabricated by the method, and its electrochemical performance, charge-discharge mechanism and the influence of coating thickness on the asymmetric electrode were analyzed. When the sulfur content of the asymmetric electrode was 63%, the specific discharge capacity was 1426 mAh g-1 at 1C ratio. After 100 cycles, the specific discharge capacity remained 990 mAh g-1 and the coulombic efficiency was 97%. In addition, the ultraviolet spectroscopy showed that the absorption peak intensity was about 0.05 after discharge and almost zero after charge, indicating that the fish-scale-based porous carbon layer limited the active substance to the positive side of the sulfur electrode to prevent its dissolution; the asymmetric electrode resistance (4.3_) was less than that of the porous carbon electrode (7.1_), indicating that the fish-scale-based carbon coating. As the upper collector, the coating provides a channel for electronic conduction and reduces the interfacial resistance. The effect of coating thickness on the electrochemical performance of lithium-sulfur batteries was studied. The suitable coating thickness was selected to improve the cycle performance and energy density of lithium-sulfur batteries. Thirdly, the preparation of ichthyosis-based graphite and its application in lithium-ion batteries. The graphitization of fish-scale graphite at 00 C and the effect of different preparation methods on the electrochemical performance of lithium ion anode were studied to reveal the mechanism of charge-discharge reaction. At the same time, low defect and high graphitization (Id/Ig=0.10) increased the first coulomb efficiency to 73.4%. In addition, high power transmission electron microscopy, Raman spectroscopy, atomic force microscopy and scanning tunneling microscopy were used to study the charge-discharge reaction mechanism. The graphite material was electrochemically stripped into 2-3 carbon atom layers by lithium ion continuous de-embedding, forming a double-layer graphene structure with A-B stacking.
【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM912;TQ127.11
，
本文编号：2195807
[Abstract]:In recent years, with the rapid development of electric vehicles, the energy density of batteries is required to be higher. Porous carbon materials have been widely used in the field of energy storage because of their excellent physical and chemical properties. Especially, carbon materials with hierarchical porous structure have obvious advantages and become a research hotspot. In order to improve the electrochemical performance of lithium-sulfur battery cathode and lithium-ion battery cathode, the preparation and characterization of fish-scale-based porous carbon were studied. Based on the composition and structure of fish-scale, inorganic materials were used as templates and organic materials as carbon sources. Carbonization and activation of fish-scale carbon materials were studied by means of SEM, XRD, Raman and XPS. The results show that the pore structure of the materials is more developed with the increase of the carbonization temperature from 600 C to 900 C. At the same time, the content of nitrogen decreased from 6.54% to 0.92%, and the content of quaternary nitrogen decreased gradually. The C/O molar ratio was 8.49 at the carbonization temperature of 900 C, indicating that the reducibility of carbide increased. Secondly, the electrochemical performance of lithium-sulfur battery cathode was improved by using fish-scale porous carbon. By means of energy dispersive spectroscopy, the kinetics of porous carbon-sulfur cathode with different structures was analyzed, and the charge-discharge reaction mechanism of fish-scale porous carbon-sulfur cathode was studied. When the carbonization temperature rises to 900C, the first discharge specific capacity is 1612 mAh g-1, and after 50 cycles, the capacity retention rate is 73.6%; the more developed the pore structure of carbide, the more easily the polysulfide is adsorbed on the cathode surface, and the utilization rate of active material is improved; when the carbonization temperature rises from 600 C to 900 C, the electrolyte resistance decreases from 5.75_to 1. 31_, high potential reduction peak and oxidation peak barrier decreased from 0.42 V to 0.22 V; with the increase of carbonization temperature, the structure of carbide became more perfect, the surface ions migrated less to the electrolyte, the diffusion decreased, the electrochemical reversibility increased, the electrode polarization decreased; at different discharge depths of O.1C and 1C times, the ultraviolet-visible spectroscopy spectrum was obtained. The maximum absorption peaks appeared at 237 nm, 265 nm and 300 nm, while S62-polysulfide ions existed steadily. The positive absorption peaks of fish-scale-based porous carbon and sulphur were less than those without addition. The results showed that fish-scale-based porous carbon could absorb active substances and improve the utilization rate of active substances in polar plates. The asymmetric electrode was designed and fabricated by the method, and its electrochemical performance, charge-discharge mechanism and the influence of coating thickness on the asymmetric electrode were analyzed. When the sulfur content of the asymmetric electrode was 63%, the specific discharge capacity was 1426 mAh g-1 at 1C ratio. After 100 cycles, the specific discharge capacity remained 990 mAh g-1 and the coulombic efficiency was 97%. In addition, the ultraviolet spectroscopy showed that the absorption peak intensity was about 0.05 after discharge and almost zero after charge, indicating that the fish-scale-based porous carbon layer limited the active substance to the positive side of the sulfur electrode to prevent its dissolution; the asymmetric electrode resistance (4.3_) was less than that of the porous carbon electrode (7.1_), indicating that the fish-scale-based carbon coating. As the upper collector, the coating provides a channel for electronic conduction and reduces the interfacial resistance. The effect of coating thickness on the electrochemical performance of lithium-sulfur batteries was studied. The suitable coating thickness was selected to improve the cycle performance and energy density of lithium-sulfur batteries. Thirdly, the preparation of ichthyosis-based graphite and its application in lithium-ion batteries. The graphitization of fish-scale graphite at 00 C and the effect of different preparation methods on the electrochemical performance of lithium ion anode were studied to reveal the mechanism of charge-discharge reaction. At the same time, low defect and high graphitization (Id/Ig=0.10) increased the first coulomb efficiency to 73.4%. In addition, high power transmission electron microscopy, Raman spectroscopy, atomic force microscopy and scanning tunneling microscopy were used to study the charge-discharge reaction mechanism. The graphite material was electrochemically stripped into 2-3 carbon atom layers by lithium ion continuous de-embedding, forming a double-layer graphene structure with A-B stacking.
【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TM912;TQ127.11
，
本文编号：2195807
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