【作者】 吴燕；

【导师】 曹景沛；

【作者基本信息】 中国矿业大学 ， 化学工艺， 2021， 博士

【摘要】 开发稳定、高效和低成本的储能器件对发展可再生能源与绿色能源具有重要意义。超级电容器作为一种新型的绿色储能器件,因具有功率密度大、充放电速率快和循环寿命长等优点而引起了广泛关注,同时也被认为是目前最有前景的储能设备之一。电极材料是影响超级电容器电化学性能的主要因素,因此,开发具有高性能的电极材料成为研究热点。废弃生物质是生活中常见的废弃资源,将废弃生物质制备成高孔隙率的多孔炭材料应用于超级电容器中,不仅可解决环境问题,还可实现生物质资源的高附加值利用。本文以固态（豆壳和木质素）和液态（生产维生素C过程中产生的废液）为原料,采用不同的方法制备出各种结构的多孔炭（分级孔结构多孔炭、球形多孔炭和氮掺杂多孔炭球）,重点研究炭材料的制备及其在超级电容器中的应用。为开发具有优异电容性能的超级电容器电极材料和废弃生物质资源的高附加值利用提供理论依据。具体研究内容如下:（1）以生物质豆壳为碳前驱体,经H₃PO₄水热炭化和KOH活化后,得到高比表面积和孔隙发达的多孔炭。H₃PO₄处理后得到的产物具有更高的碳含量,有利于后期活化反应的进行。经H₃PO₄水热炭化活化所得多孔炭（PC）的比表面积是未经H₃PO₄处理活化所得多孔炭（SSC）的1.95倍,且具有更多的有利于电解质传输的2～5 nm范围的介孔。用PC作为电极材料用于超级电容器中所表现出的电化学性能明显优于SSC,在6 M KOH电解质两电极体系中显示出高的比电容(0.1 A g^-1的电流密度下比电容高达301 F g^-1)和优良的稳定性（经15000循环后比电容保持率为93.8%）。（2）以木质素为碳前驱体,经Zn Cl₂溶液水热炭化和KOH活化后得到微孔、中孔相互连接的蜂窝状多孔炭。Zn Cl₂水热处理后所得多孔炭呈现出蜂窝状结构,而未加Zn Cl₂所得多孔炭显示出块状结构,表明Zn Cl₂溶液加入影响所得多孔炭的形貌结构。活化温度升高和KOH用量增加都会导致多孔炭比表面积增加且孔径向孔宽的方向发展。但是,过高的温度和过量的KOH都会因为过度活化导致多孔炭的比表面积减小。在6 M KOH电解质的两电极体系中,活化温度为600 ^oC和碱炭比为5得到的多孔炭（0.5-HPC-600-5）比电容高达384 F g^-1(0.04 A g^-1),电流密度扩大125倍后比电容仍高达239 F g^-1。此外,其能量密度为10.48 Wh kg^-1和2 A g^-1的电流密度下经10000次循环后比电容保持为最初的96.96%（优异的循环稳定性）。（3）以生产维生素C过程中产生的废液为碳前驱体,三聚氰胺泡沫为模板,经炭化活化两步法得到具有超高比表面积的网络状结构的多孔炭,将其用于超级电容器中展现出优异的电化学性能。以1-乙基-3甲基咪唑四氟硼酸盐（EMIMBF₄）离子液体为电解质所组装的电容器工作电压达到3.8 V,且多孔炭表现出高的比电容(在电流密度为0.1A g^-1时比电容为217 F g^-1)、优异的倍率性能(30 A g^-1电流密度下比电容仍高达94 F g^-1)、出色的循环稳定性(在电流密度为5 A g^-1下循环10000次比电容保持率为89%)和高的能量密度(107 Wh kg^-1)。另外,将多孔炭作为电极材料组装到固态电容器中,同样具有良好的电容性能,在0.5 A g^-1电流密度时比电容为180 F g^-1和长循环寿命(10 A g^-1电流密度下循环10000次后比电容保持率为85%)。（4）以生产维生素C过程中产生的废液为碳前驱体,经水热炭化和K₂Fe O₄活化后得到具有球形结构的多孔炭,并探究K₂Fe O₄用量对多孔炭球的孔隙结构的影响。所制备的样品呈现出球形结构且具有分级孔隙（丰富的微孔和一定的中孔）的孔结构,且随着K₂Fe O₄用量增加,所得多孔炭球的孔径向着孔宽的方向发展。将多孔炭球用于水系电解质超级电容器中表现出高的比电容、优异的循环稳定性和良好的倍率性能。同时,在以PVA/KOH为电解质的固态电容器中,多孔炭球也展示出高的比电容(在0.1 A g^-1电流密度下比电容为196 F g^-1)和良好的循环稳定性（10000次循环后比电容保持率为82.6%）。此外,以1-乙基-3甲基咪唑四氟硼酸盐（EMIMBF₄）作为电解质组装的电容器的工作电压达到3.8 V,能量密度最高达47.2 Wh kg^-1且经10000次循环后比电容保持率为88.9%。（5）杂原子的掺杂能够提高超级电容器的电容性能,在高铁酸钾（K₂Fe O₄）活化的过程中,引入尿素（作为氮源）,制备了具有丰富氮掺杂的多孔炭球。在活化的过程中引入尿素,能够成功的将氮引入到多孔炭球中,其氮含量高达3.9 wt.%。在活化的过程中尿素可能会演变为氮化碳,氮化碳分解产生气体从炭材料中释放出,因此,制备的氮掺杂多孔炭比表面积高达2796 m² g^-1（NPCS-700）。所制备的多孔炭球NPCS-700具有丰富的在孔径为1～2 nm范围内的大微孔和3～5 nm范围内的介孔。将NPCS-700应用于不同电解质中都展示出良好的电化学性能。在6 M KOH电解质中,NPCS-700具有优异的循环稳定性,6000次充放电循环后的比电容保持率为97.1%和最高的比电容为316 F g^-1。在1 M Na₂SO₄和离子液体（EMIMBF₄）中工作电压窗口分别可达1.8 V和3.8 V,其能量密度分别可达20.2 Wh kg^-1和85.5 Wh kg^-1。NPCS-700在不同电解质中的电化学性能有差异,主要是电解质的离子尺寸、离子电导率以及多孔炭的孔隙结构与电解质离子的匹配程度的差异导致。该论文有100幅图、26个表和270篇参考文献。更多还原

【Abstract】 Developing stable,efficient and low-cost energy storage devices is a great significance for the development of renewable energy and green energy.As a new type of green energy storage device,supercapacitor has attracted wide attention due to its high power density,fast charge and discharge rate,long cycle life.In addition,supercapacitor is also considered as one of the most promising energy storage devices.The electrochemical performances of supercapacitor is affected by the electrode materials.Development of electrode materials with high performance have become one of research hotspot to study the supercapacitor.Waste biomass are common waste resources in life.It can not only solve environmental problems,but also realize the high value-added utilization of biomass resources by using the waste biomass to prepare porous carbon materials with high porosity.In this paper,hierarchically porous carbon,spherical porous carbon and nitrogen doped porous carbon had been derived from waste biomass,such as solid（soybean shell and lignin）and liquid（waste liquid produced in the process of vitamin C production）.The preparation and application of porous carbon have been researched emphatically.It provides a theoretical basis for the development of supercapacitor electrode materials with excellent capacitance performance and the high value-added utilization of waste biomass resources.This thesis mainly contains the following content:（1）Soybean shell is converted into porous carbon with high specific surface area and well-developed pore structure via hydrothermal carbonization with H₃PO₄ followed by KOH activation.The product obtained from the hydrothermal carbonization with H₃PO₄possesses more carbon content,which is beneficial to the KOH activation reaction.The specific surface area of activated porous carbon（PC）after H₃PO₄ treatment is 1.95 times of that of untreated porous carbon（SSC）.And the PC also has more pore in the range of 2～5 nm,which is conducive to electrolyte transport.Compared with the SSC,PC used as the electrode materials for supercapacitor has better electrochemical performance.In the two-electrode system,the specific capacitance of PC can reach upto 301 F g^-1at the current density of 0.1 A g^-1 in 6 M KOH.And PC also exhibits excellent cycling stability with the specific capacitance remaining at 93.8%after15000 cycles.（2）The porous carbon with honeycomb structure was obtained by hydrothermal carbonization of Zn Cl₂ solution followed KOH activation.The porous carbon obtained by Zn Cl₂solution hydrothermal carbonization show honeycomb structure,while the porous carbon without Zn Cl₂ show block structure,indicating that adding Zn Cl₂ solution affects the morphology of porous carbon.Specific surface area of porous carbon increase and the pore towards to the width pore with the increasing the activation temperature and activation ratio.However,excessive high temperature and activation ratio will cause the decrease of specific surface area of porous carbon due to over activation.The sample obtained at 600 ^oC activation temperature and activation ratio of 5（0.5-HPC-600-5）has the high specific capacitance of 384F g^-1(0.04 F g^-1)and the specific capacitance is still maintain 239 F g^-1 at the current density of5 A g^-1.Moreover,0.5-HPC-600-5 possesses high energy density of 10.48 Wh kg^-1 and specific capacitance remaining at 96.96%after 15000 cycles.（3）The interconnected network structure pore with super high specific surface area was obtained by using melamine foam as template and waste liquid（by-product from the process of vitamin C production）through carbonization and activation two step method.The porous carbon used as electrode materials for supercapacitor show outstanding electrochemical performances in EMIMBF₄ and the working voltage can reach 3.8 V.The porous carbon shows a high specific capacitance(217 F g^-1 at the current density of 0.1 A g^-1),excellent rate performance(the specific capacitance is as high as 94 F g^-1 at 30 A g^-1),excellent cycle stability(specific capacitance remaining at 89%after 10000 cycles in 5 A g^-1)and ultra-high energy density(107 Wh kg^-1).In addition,the porous carbon also has electrochemical performance in all-solid-state symmetric supercapacitor.（4）The porous carbon spheres are obtained from waste liquid via hydrothermal treatment followed with K₂Fe O₄ activation.The results show that the prepared samples have spherical structure and hierarchical pore structure（rich micropores and a certain of mesopores）.The pore size tends to the direction of pore width with the increase of K₂Fe O₄ content.The prepared porous carbon spheres show high specific capacitance,excellent cycle stability and good rate performance in aqueous electrolyte.At the same time,in the solid-state capacitor with PVA/KOH as electrolyte,the porous carbon spheres also showed high specific capacitance(196 F g^-1 at 0.1A g^-1)and good cycle stability（82.6%specific capacitance retention after 10000 cycles）.In order to improve the energy density of the supercapacitor,the symmetric supercapacitor is assembled with ionic liquid（EMIMBF₄）as electrolyte and the working voltage of supercapacitor reaches3.8 V.The energy density of supercapacitor is 47.2 Wh kg^-1 and excellent cycle performance（the specific capacitance retention is 88.9%after 10000 cycles）.（5）The N-doped can improve the capacitive performance.In order to promote the electrochemical performance of porous carbon spheres,urea（as N source）was introduced during the K₂Fe O₄ activation process to prepare porous carbon spheres with high N content.The results show that the N has been successfully doped in the porous carbon spheres.The N content in the NPCS-700 is as high as 3.9 wt.%.In addition,urea maybe convert into carbon nitride,which is decomposes to generate gas and released from carbon materials under high activation temperature during the activation process.Therefore,the specific surface area of NPCS-700 is reach upto 2796 m² g^-1.In addition,NPCS-700 also possesses abundant large micropore（the pore side in the 1～2 nm）and the mesopore in the pore range of 3～5 nm.When NPCS-700 used as electrode material for supercapacitor,it shows good electrochemical performance in different electrolyte.In 6 M KOH,NPCS-700 exhibits excellent cycle stability（the specific capacitance retains 97.1%of initial capacitance after 6000 cycles）and the specific capacitance is as high as316 F g^-1.The working voltage in 1 M Na₂SO₄ and EMIMBF₄ can reach 1.8 V and 3.8 V,respectively.The energy density of NPCS-700 is as high as 20.2 Wh kg^-1 and 85.5 Wh kg^-1 in 1M Na₂SO₄ and EMIMBF₄,respectively.The electrochemical performance of NPCS-700 in different electrolytes is different owing to the different of ion size,ionic conductivity,the matching degree between pore structure of porous carbon and electrolyte ions.This thesis contains 100 Figures,26 Tables and 270 references.更多还原