介孔过渡金属氮化物纳米线的制备、电容特性及其柔性超级电容器

Flexible all-solid-state supercapacitors (SCs) have great potential in flexible and wearable electronics due to the safety, flexibility, high power density, and portability. The energy storage properties of SCs are determined mainly by the composition, conductivity of electrode materials, as well as the configuration of the integrated electrode. Carbon electrodes have a high power density, fast charging and discharging rates, and long cycle lifetime, however, they generally suffer from a small energy density due to the low specific capacitance (20-250 F/g) of carbon-based electrodes. Metal oxides and conducting polymers generally deliver a high specific capacitance. However, the low electrical conductivity of metal oxides and instability intrinsically associated with conductive polymers generally lead to poor rate capability, low power density, and/or poor cycling stability. In this project, nanostructured early transition metal nitrides that have good electrical conductivity like metals and large specific capacitances comparable to those of many metal oxides will be prepared. The electrolyte ions participating in the charge storage reaction will be identified by a series of ion isolation and substitution cyclic voltammetry experiments. The effect of composition, N/O ratio, and surface chemical states on the electric double layer capacitance and pseudocapacitance will be systematically studied and capacitive evolution trends from early transition metal oxides to nitrides will be revealed. The changes of electrode composition and surface chemical states during charge and discharge will be characterized using in-situ Raman spectroscopy. The electron count will be established by using a Nernstian equation to relate the rest potential to the active ion concentration. The specific charge transfer events and charge storage mechanism on nanostructured early transition metal nitrides during charge storage will be described. Additionally, a facile and versatile method for flexible, high-performance nanohybrid films consisting of alternating stacked one-dimensional (1D) mesoporous metal nitrides and reduced graphene oxide (MMNs/rGO) is provided. In this architecture, the mesoporous metal nitrides nanowires provide a large surface area and abundant active sites for charge storage and the rGO nanosheets provide robust mechanical and flexible support while retaining the intrinsic rigidity of MMNs. Hence, excellent capacitive properties and robust flexibility and mechanical integrity are accomplished. The high-performance all-solid-state flexible SCs based on freestanding MMNs/rGO were fabricated and the capacitive properties will be systematically investigated. Being flexible, environmentally friendly, and easily connected in series and parallel, the all-solid-state SCs have promising potentials in portable/wearable electronics.

柔性超级电容器是一种重要的储能器件，在可穿戴和便携式柔性电子产品以及新能源等领域具有重要的应用前景。电极材料决定超级电容器的储能性能。针对碳电极材料比容量低和金属氧化物导电性差的问题，本项目拟制备出具有高导电性和大比电容的介孔过渡金属氮化物纳米线。采用离子分离和替代的电化学测试方法，识别电解液中的何种离子参与过渡金属氮化物纳米线的赝电容反应。考察过渡金属氮化物纳米线的形貌、组成、表面化学状态和导电性对双电层电容和赝电容的影响。结合原位Raman光谱，分析充放电过程中过渡金属氮化物纳米线的形貌、组成以及表面化学状态的变化，揭示过渡金属氮化物表面赝电容产生的电化学机制和电子转移过程。利用静电自组装和真空抽滤的方法，制备出过渡金属氮化物纳米线/还原氧化石墨烯复合柔性多层膜电极，研究其柔性储能性能，开发出基于过渡金属氮化物纳米线的高性能柔性膜电极和超级电容器，促进柔性储能器件的发展和应用。

柔性超级电容器是一种重要的储能器件，电极材料是超级电容器的核心，决定其储能性能。本项目围绕介孔结构金属过渡金属氮化物电极材料的可控制备、电容性能、过渡金属氮化物/石墨烯复合柔性膜电极和全固态柔性超级电容器等开展研究工作。发展了拓扑化学合成法，利用一维金属氧化物纳米材料为前驱物，通过简单氮化处理，获得了高导电性和大比电容的介孔过渡金属氮化物纳米线。考察了氮化温度、反应时间等对过渡金属氮化物电极材料的形貌、结构、组成、导电性和电容性能的影响，结合原位Raman光谱和电化学表征结果，提出了过渡金属氮化物表面赝电容产生的电化学机制。发展了制备自支撑过渡氮化物基柔性电极的新方法，将石墨烯（rGO）作为“交联剂”与过渡氮化物纳米线层层复合，获得了自支撑过渡金属氮化物/rGO柔性复合膜电极，组装了过渡金属氮化物基高能量密度和高功率密度全固态柔性超级电容器。设计合成了介孔过渡金属氮化物/碳复合硫载体材料，利用过渡金属氮化物高导电性、强极性和催化活性，抑制多硫化物的穿梭，加速其催化转化，提高了硫正极电化学利用率、容量和倍率性能，获得了大容量、高倍率和长寿命的锂硫电池正极材料。发明了原位固-固相分离制备金属粒子/过渡金属氮化物复合催化剂的新方法，获得了具有优异电解水制氢和氧还原性能的电催化剂。设计合成了新型锂（钠）离子电池大容量合金负极材料和适用于大体积膨胀合金负极的粘结剂。本项目的研究，在高性能介孔金属氮化物电极材料、电容储锂机理、柔性超级电容器、高比能锂硫电池、电催化剂以及锂离子电池合金负极材料等领域取得了一系列创新研究成果，促进了柔性超级电容器和高比能储能器件的发展和应用。