鋰電池用魚鱗基炭材料的制備與表征
發(fā)布時(shí)間：2018-08-21 12:59
【摘要】：近年來(lái),電動(dòng)車飛猛發(fā)展,對(duì)電池能量密度提出更高要求。由于多孔炭材料優(yōu)異的理化性能,因此被廣泛地應(yīng)用于儲(chǔ)能領(lǐng)域,特別是具有分級(jí)孔結(jié)構(gòu)的炭材料優(yōu)勢(shì)顯著,已經(jīng)成為目前研究熱點(diǎn)。本文采用廢棄物魚鱗為原料,設(shè)計(jì)制備出具有分級(jí)孔結(jié)構(gòu)炭材料,并進(jìn)一步將其石墨化制備了魚鱗基石墨,目的為提高鋰-硫電池正極和鋰離子電池負(fù)極電化學(xué)性能。具體工作包括：第一,魚鱗基多孔碳的制備與表征。憑借魚鱗的組成和結(jié)構(gòu)優(yōu)勢(shì),以無(wú)機(jī)物為模板,有機(jī)物為碳源,制備了魚鱗基多孔炭材料,并采用SEM、XRD、Raman、XPS等手段研究魚鱗炭材料的碳化與活化過(guò)程。結(jié)果表明,隨著碳化溫度從600℃增加至900℃,炭材料的孔結(jié)構(gòu)更發(fā)達(dá)。當(dāng)碳化溫度為900℃時(shí),比表面高達(dá)2732 m2 g-1；ID/IG值從1.40降到1.20,石墨化度增加,缺陷度減少；同時(shí),氮元素含量從6.54%降低到0.92%,季氮含量逐漸減少；碳化溫度為900℃時(shí),C/O摩爾比為8.49,表明炭化物還原性增加。第二,用魚鱗基多孔炭提高鋰-硫電池正極電化學(xué)性能。借助交流阻抗、循環(huán)伏安、紫外分光光譜、X射線能量色散譜分析等手段,分析不同結(jié)構(gòu)的多孔炭硫正極動(dòng)力學(xué),研究魚鱗基多孔炭硫正極的充放電反應(yīng)機(jī)制,并對(duì)電解液組成與倍率及不同放電深度的關(guān)系進(jìn)行表征。研究表明,當(dāng)碳化溫度為600-7000C,放電比容量基本維持在500-700mAh g-1。當(dāng)碳化溫度提升至9000C時(shí),首次放電比容量為1612mAh g-1,經(jīng)過(guò)50次循環(huán)后,容量保持率為73.6%；炭化物孔隙結(jié)構(gòu)愈發(fā)達(dá),多硫化物更易被吸附在正極表面,活性物質(zhì)利用率得到提高；當(dāng)碳化溫度從600℃增加到900℃,電解液電阻從5.75 Ω降至1.31Ω,高電位還原峰與氧化峰位壘從0.42V降至0.22V；在充放電過(guò)程中,隨著碳化溫度增加,炭化物結(jié)構(gòu)更完善,表面離子更少地遷移到電解液中,擴(kuò)散減小,電化學(xué)可逆性增加,電極極化減��；在O.1C及1C倍率不同放電深度,紫外可見(jiàn)分光光譜在237nm、265nm及300nm均出現(xiàn)最大吸收峰,而S62-多硫離子穩(wěn)定存在,魚鱗基多孔炭硫正極吸收峰強(qiáng)度小于不添加的吸收峰,表明魚鱗基多孔炭能夠吸附活性物質(zhì),提高極片活性物質(zhì)利用率。憑借魚鱗基多孔炭的結(jié)構(gòu)和組成優(yōu)勢(shì),通過(guò)冷凍干燥法設(shè)計(jì)并制備非對(duì)稱電極,對(duì)其電化學(xué)性能,充放電機(jī)制以及涂覆層厚度對(duì)非對(duì)稱電極的影響進(jìn)行分析研究。當(dāng)非對(duì)稱電極的硫含量為63%時(shí),1C倍率下,首次放電比容量為1426 mAh g-1;經(jīng)過(guò)100次循環(huán)后,比容量仍保持990 mAh g-1,庫(kù)侖效率高達(dá)97%。此外,根據(jù)紫外分光光譜結(jié)果顯示,放電后吸收峰強(qiáng)度在0.05左右,充電后吸收峰強(qiáng)度幾乎為零,表明魚鱗基多孔炭層將活性物質(zhì)限制在硫正極一側(cè),阻止其溶解；非對(duì)稱電極電阻(4.3 Ω)小于添加多孔炭電極電阻(7.1 Ω),表明魚鱗基炭涂覆層作為上層集流體,為電子傳導(dǎo)提供通道,減小界面電阻；研究涂覆層厚度對(duì)電池電化學(xué)性能的影響,選擇適合涂覆層厚度,提高鋰-硫電池循環(huán)性能以及能量密度。第三,魚鱗基石墨的制備及其在鋰離子電池的應(yīng)用。以魚鱗為前驅(qū)體,2800℃石墨化,制備魚鱗基石墨。研究不同制備方法的結(jié)構(gòu)變化規(guī)律,以及對(duì)鋰離子負(fù)極電化學(xué)性能影響,以揭示充放電反應(yīng)機(jī)制。研究表明所制備石墨材料的I2D/IG比值為1.57,比表面積為5.1 m2g-1,平均孔徑為17.1 nm,(002)晶面間距0.337nm,有利于鋰離子的嵌入和脫出；同時(shí),材料低缺陷度和高石墨化度(Id/Ig=0.10)將首次庫(kù)侖效率提高至73.4%；此外,采用高倍透射電鏡、拉曼譜圖、原子力顯微鏡及掃描隧道顯微鏡等分析手段對(duì)充放電反應(yīng)機(jī)制進(jìn)行初探,結(jié)果表明在一定電流密度下,鋰離子不斷地脫嵌將所制備石墨材料電化學(xué)剝離成2-3個(gè)碳原子層,形成具有A-B堆疊的雙層石墨烯結(jié)構(gòu)。
[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.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TM912;TQ127.11
，
本文編號(hào)：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.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TM912;TQ127.11
，
本文編號(hào)：2195807
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