锂离子电容器继承了超级电容器高功率性能和锂离子电池高能量密度两者的优点.然而,高电化学性能电极材料的短缺以及正负电极材料动力学的不匹配是构筑高能量/高功率密度锂离子电池遇到的最大挑战.我们通过简单的溶液组装和煅烧法得到了具有核壳结构的Fe3O4@NC复合材料.首先,研究了不同热解温度得到的Fe3O4@NC样品的储锂性能.结构单元纳米化和丰富的微孔使得Fe3O4@NC-700具有大比表面积,同时暴露出更多的活性位点,缩短了离子传输路径,表现出特殊的赝电容行为,从而显著提高了储锂动力学.除此之外,N-掺杂的碳壳提供了较高的电子导电性并保证了在循环测试中的结构完整性.以Fe3O4@NC-700为负极,膨胀石墨烯EGN为正极,1 mol L^-1Li PF6为电解液,组装成锂离子电容器.受益于正负电极相配的动力学以及Fe3O4@NC-700和EGN两者的协同优势,Fe3O4@NC-700//EGN杂化离子电容器获得了较宽的工作电压窗口(1.0–4.5 V),比能量最高可达137 W h kg^-1,比功率最高可达8.2 k W kg^-1,且循环稳定性出色.本工作可为下一代兼具高比能量和高比功率的新型混合能源存储系统的设计提供启示.
H+-restacked nanosheets and nanoscrolls peeled from K4Nb6O17display different structures and surface characters. The two restacked samples with increased surface areas have an amazing visible-light response for the photodegradation of dyes, which is superior to commercial TiO2(P25) and Nb2O5. By comparison, H+/nanosheets have a relatively faster photodegradation rate originated from large and smooth basal plane.The work reveals that dye adsorbed on the unfolded nanosheets can effectively harvest sunlight. Due to facile preparation, low-cost and high photocatalytic efficiency, H+/nanosheets and H+/nanoscrolls might be used for the visible light-driven degradation of organic dyes as a substitute for TiO2in industry.
High energy density and enhanced rate capability are highly sought-after for supercapacitors in today's mobile world.In this work,polyaniline/titanium carbide(MXene)(PANI/Ti3C2Tx)nanohybrid is synthesized through a facile and cost-effective self-assembly of.one-dimensional(10)PANI nanofibers and two-dimensional(20)Ti3C2Tx nanosheets.PANl!Ti3C2Tx delivers greatly improved specific capacitance,ultrahigh rate capability(67%capacitance retention from 1 to 100 A·g^(-1))as well as good cycle stability.Electrochemical kinetic analysis reveals that PANI/Ti3C2Tx is featured with surface capacitance-dominated process and has a quasi-reversible kinetics at high scan rates,giving rise to an ultrahigh rate capability.By using PANl!Ti3C2Tx as positive electrode,an 1.8 V aqueous asymmetric supercapacitor(ASC)is successfully assembled,showing a maximum energy density of 50.8 Wh·kg^(-1)·(at 0.9 kW-kg-1)and a power density of 18 kW·kg^(-1)(at 26 Wh·kg^(-1)).Moreover,an 3.0 V organic ASC is also elaborately fabricated,·by using PANI/Ti3C2Tx,achieving an ultrahigh energy density of 67.2 Wh·kg^(-1)(at 1.5 kW·kg^(-1))and a power density of 30 kW·kg^(-1)·(at 26.8 Wh·kg^(-1)).The present work not only improves fundamental understanding of the structure-property relationship towards ultrahigh rate capability electrode materials,but also provides valuable guideline for the rational design of high-performance:energy storage devices with both high energy and power densities.
