【作者】 黄岚；

【导师】 沈培康；

【作者基本信息】 广西大学 ， 材料工程（专业学位）， 2018， 硕士

【摘要】 超级电容器以充电效率高、循环寿命长、使用温度范围宽、贮存寿命长、体积比容量及质量比容量高、体积小、环境友好等优异性能而引起了社会的广泛关注。碳材料由于其原料来源广泛、低价环保、比表面积大、导电性良好、工作温度范围较宽和稳定性较高,而成为目前应用最广的超级电容器电极材料。但其应用于商业超级电容器的体积能量仅为5-6 WhL-1,在实际应用中受到了限制。氟掺杂碳由于具有高容量和高速率能力,而成为超电容器电极材料极具吸引力的候选电极材料。然而,氟掺杂碳的合成通常需要高度危险或昂贵的含氟的反应物,而且由于碳的氟吸收水平较低,而导致效率很低。本论文采用聚四氟乙烯(PTFE)为氟源,引入了一种有效的氟掺杂碳的方法。本论文以镍离子交换树脂为碳源,设计合成了石墨化多孔碳材料,另外,以聚四氟乙烯(PTFE)为氟源,商业活性碳和镍离子交换树脂为碳源,分别制备出氟掺杂碳材料,并研究了它们在有机系超级电容器电极材料中的应用,主要研究内容和结果如下:(1)提出一种简单的低温石墨化多孔碳材料制备方法,即往碳源中添加催化剂NiCl2和造孔剂KOH,在较低温度下(<1000℃)进行烧结从而制备出石墨化多孔碳材料。此方法与传统的高温烧结法相比,石墨化温度大大降低,节约了生产成本,制备的石墨化多孔碳材料比表面积较大。(2)通过采用上述制备的石墨化多孔碳材料,我们将其应用于有机系超级电容器电极材料,制备出不同厚度的电极片进行测试。在0.25 A cm-3的体积电流密度下,电极片为50 μm的HPG的电池体积比电容和单电极体积比电容分别为10.2Fcm-3和61 Fcm-3,单电极质量比电容为120.5 Fg-1,而在2.5 Acm-3较大体积电流密度下,其电容保持率高达94.1%,具有良好的倍率性能,且在1.5 Acm3体积电流密度下循环10000圈,体积比电容保持率可达81.5%。(3)关于氟掺杂碳,我们介绍两种合成方法:一种是将PTFE粉末直接与商业活性碳混合,惰性气体保护下于800℃一步合成氟掺杂商业活性碳(AC-F),另一种是将PTFE粉末直接与Ni交换的树脂粉末混合,以KOH为造孔剂,惰性气体保护下于800℃一步合成氟掺杂石墨化多孔碳材料(HPG-F)。将这两种氟掺杂碳应用于超级电容器电极材料,AC-F和HPG-F均优于不含氟的碳材料,在高功率循环中多产出40%的电池体积能量。考虑到集流体和隔膜所占的体积分数,电极片厚度为100 μm和50 μm的AC-F 在 0.1 kW L-1-2.15 kW L-1 下分别产出 12.9 Wh L-1-6.7 Wh L-1。在1.5 A cm-3的体积电流密度下循环10000圈,其电容保持率高达97.1%。F的掺杂可以有效提高碳材料的电化学性能,这与氟的高电负性有密不可分的关系。此外,简单的合成方法也很有可能以同样的方式进一步改进其他超级电容器。更多还原

【Abstract】 Supercapacitors are of great interest in modern society due to their high charging efficiency,long cycle life,wide operating temperature range,long cycle life,high volumetric and specific capacitances,small volume and environmental friendliness.Carbon is currently the most widely used supercapacitor electrode material due to its wide source of raw materials,low cost,environmental protection,large surface area,good conductivity,wide operating temperature range and high stability.However,its volume energy used in commercial super capacitors is only～5 to 6 Wh L-1,which is limited in practical application.Fluorine-doped(F-doped)carbons are attractive candidates for supercapacitor electrode material owing to their high capacitance and high rate capability.However,synthesis of F-doped carbons typically requires highly hazardous or expensive fluorine-based reactants and has low efficiency due to low levels of fluorine uptake by the carbon.In the present study,we introduce an effective means to F-doped carbon using polytetrafluoroethylene(PTFE)pyrolysis.In this thesis,nickel ion exchanged resin was used as a carbon source to synthesize graphitized porous carbon.In addition,fluorine-doped carbon materials were prepared with PTFE as fluorine source and commercial activated carbon and nickel ion exchange resin as carbon source,and their applications in organic supercapacitor electrode materials were studied.The main research contents and results are as follows:(1)In the first chapter,the simple synthesis of low-temperature graphitized porous carbon material from a Ni-ion exchanged resin is described.NiCl2 is added to the carbon source as catalyst and KOH as pore-forming agent to produce highly porous graphite(HPG)at low temperature(<1000 ℃).Compared with the traditional high temperature sintering method,the use of NiCl2 lowers graphitization temperature and saves the production cost greatly.Besides,the graphitized porous carbon material prepared has a larger specific surface area.(2)HPG is evaluated as an organic supercapacitor electrode material by different electrode thickness.HPG at 50-μm film thickness produced the total cell and material volumetric capacitance of 10.2 and 61 F cm-3 respectively,while the material specific capacitance was 120.5 F g-1 at volumetric current of 0.25 A cm-3.HPG exhibited the capacitance retention of 94.1%at high volumetric current of 2.5 A cm-3,undoubtedly indicating an excellent rate capability.Besides,HPG revealed good extraordinary cycling stability with the capacitance retention of 81.2%at volumetric current of 1.5 A cm’3 after 10,000 cycles.(3)In the second chapter,we demonstrate two possible means of synthesizing F-doped carbon using polytetrafluoroethylene(PTFE)pyrolysis:firstly,by directly pyrolyzing the polytetrafluoroethylene(PTFE)mixed AC in the presence of the nitrogen atmosphere under 800 ℃ to produce AC-F,and secondly by direct synthesis of an F-doped highly porous graphite(HPG-F)in the same environment.As supercapacitor electrode materials in organic electrolyte,both AC-F and HPG-F outperform their non-F-doped counterparts,delivering up to 40%gain in cell volumetric energy at high power cycling.Considering current collector and separator volume fractions,cells containing AC-F electrode films of 100 and 50 μm deliver an impressive 12.9 Wh L-1 at 0.1 kW L-1 and 6.7 Wh L-1 at 2.15 kW L-1 respectively,and cells containing AC-F electrode films of 100 μm revealed excellent extraordinary cycling stability of the capacitance retention of 97.1%at volumetric current of 1.5 A cm-3 after 10,000 cycles.F doping can effectively improve the electrochemical performance of carbon materials,which is closely related to the high electronegativity of fluorine.In addition,it is likely that simple synthesis methods will further improve other supercapacitors in the same way.更多还原