织构碳纤维表面孔缺陷诱导生长多尺度氧化铁及界面耦合增强电容性能

Iron oxides have emerged as one of promising negative electrode in configuring asymmetric capacitors (ASCs) due to their variable oxidation states, nature abundance, non-toxicity and high theoretical capacitance in alkaline solution. However, the low specific capacitance, poor electrical conductivity and limited cycling stability have restricted them serving as high-performance negative electrodes in ASCs..Hollow carbon fiber textile (CFT) is composed of hollow carbon fibers bundles that are inter-woven together. It possesses a remarkable electronic conductivity, excellent mechanical flexibility and good ion penetrability. These structural properties make conductive CFT one of attractive substrates for growing iron oxides to achieve an improved capacitive performance..In this project, large-area and flexible CFT substrate will be prepared by carbonization of cellulose textile. Through further chemical activation, electrochemical oxides, nitrogen plasma or NH3/H2 reduction treatment, nanopores or cavities with N, O groups enriched on their edges will be created on the CFT surface. In this way, we anticipate to offer more nucleation sites for favorable growth of iron oxides at the cavities, which is believed to enhance the interfacial coupling between iron oxides and CFT, thus facilitating charge transfer and improving the cycling stability of composite electrode during repeated charge-discharge processes. Through further control over the solvents polarity, selective adsorption of surfactants on the facets of iron oxides in the solvothermal synthesis or electrochemical deposition, the iron oxides with quantum dots, nanofibers, nanoflakes or core-shell structures will be fabricated. Charge storage mechanism, the correlation between the structure of iron oxides and their capacitive behavior will be systematically investigated. The effect of surface functional groups, the porosity/cavity in CFT substrate on the rate capability and cycling stability of iron oxides will be analyzed and discussed. .By taking the structures, coupling modes of iron oxides on TCC, and their capacitive performances into accounts, an optimized CFT-iron oxides interfacial structure that can favor both ion and electron transport will be presented. Moreover, using the structurally optimized CFT-iron oxides as negative electrode, a solid-state asymmetric capacitor with high energy density will be configured and its practical performance will be systematically investigated. We believe that results in this project could provide new insights for rational design of high-performance flexible negative electrode towards high-energy-density asymmetric supercapacitors.

氧化铁具有高的理论比电容，是极具发展潜力的不对称电容器负极材料。针对该电极实际比电容低、导电性弱等制约其性能的突出问题，本项目拟通过碳化纤维素织物，制备兼具密集、导电及丰富离子通道的织构碳纤维柔性基底；采用化学活化在基底表面创制不同密度的孔缺陷，通过电化学氧化及等离子体刻蚀等技术调控孔缺陷周围N、O官能团浓度，促进与氧化铁前驱体离子配位，诱导其在孔缺陷区域成核生长，增强界面耦合，提高复合电极导电和循环性能；利用溶剂热合成/电化学沉积过程中溶剂极性的差异及表面活性剂在氧化铁晶面上的选择性吸附，实现织构碳纤维表面孔缺陷诱导生长高载量、多尺度氧化铁，揭示生长机理，提高比电容；阐明碳基底-氧化铁界面键合方式(配位键/范德华力)及接触形态(点/线/面)对增强氧化铁倍率性能和循环稳定性的内在机制；通过构建全固态不对称柔性电容器器件，提高能量密度，为设计高性能不对称电容器负极材料提供理论指导和技术支持。

针对氧化铁与碳基底界面作用较若而导致比电容低、稳定性差等问题，项目以碳化纯棉布为出发点，通过碳纳米管生长、电化学活化、导电高分子功能化等技术，获得了兼具柔韧、导电及丰富离子通道的织构碳纤维柔性基底；利用碳纤维表面天然螺旋褶皱结构及氧化后产生的-COOH、-OH基团与过渡金属Fe2+、Ni2+、Co3+的相互作用，在碳基底上生长了Fe2O3、FeOOH、CoNiO2等赝电容材料，研究了界面耦合及碳包覆对复合电极导电、容量、倍率及循环稳定的影响规律，构建了系列全固态不对称超级电容器，研究了器件在不同应力下的结构变化及电化学行为；在海绵碳纤维上生长了具有赝电容特征的NiCo2S4纳米片，发现了NiCo2S4纳米片与碳纤维界面强相互作用，是实现不同压缩状态下导电性稳定的关键；基于碳基底表面官能团与过渡金属离子强相互作用以增强赝电容材料-碳基底界面耦合原理，进一步通过电化学沉积技术在织构碳纤维上生长了具有丰富面内孔道的NiCo-LDH纳米片，研究了纳米片的生长机理，发现NiCo-LDH的纳米片的面内纳米孔道可显著提高电极的利用效率和离子穿透能力，为高载量下NiCo-LDH纳米片的高效利用及快速储能提供创新方法；在织构碳纤维表面电化学生长了KNb3O8基电极材料，研究了KNb3O8在KOH水系电解质中及LiPF6有机电解质中的电荷存储机制，丰富了KNb3O8的制备方法学，拓宽了KNb3O8在储能领域的应用。.上述研究成果在J. Mater. Chem. A, ACS Appl. Mater. Interfaces, J. Power Sources, Small Structures, ACS Sustainable Chem. Eng., J. Phys. Chem. C等上发表研究论文16篇，含前内封面论文1篇（Small Structures, 2021, 2, 2100029），论文他引330次。授权发明专利5件，培养博士研究生1名，硕士研究生8名。受国家留学基金委奖学金资助，1名研究生赴西班牙马德里材料科学研究所继续攻读博士学位，1名在读博士生赴荷兰代尔夫特理工大学交流学习一年；项目负责人受邀参加国内电化学储能相关会议16次，做邀请报告/口头报告15次；作为骨干成员，项目负责人入选“储能材料与器件”陕西省第二批“三秦学者”创新团队支持计划。.