柔性钛箔上生长的自支撑TiO2@NiCo2S4阵列复合材料用作高性能非对称超级电容器电极（英文）

Self-supporting TiO2@NiCo2S4 Arrays Composite on the Flexible Ti Foil for a High-performance Asymmetric Supercapacitors

近年来,随着可穿戴电子技术的出现,制作出质量轻、灵活性强的电子设备也越来越受到人们的重视,相应具有可穿戴功能的高电化学性能的储能设备也备受关注。其中,超级电容器具有循环寿命长、充放电速度快、功率密度高等优点,是一种很有前途的储能设备。因此,柔性超级电容器的设计和生产被认为是满足先进柔性电子设备需求的最有前途的策略之一。鉴于电极材料是影响超级电容器的性能和生产成本的关键因素,因此开发高性能和低成本的电极材料是超级电容器研究的重要内容。在众多研究的电极材料中,双金属化合物因具有较高的理论比电容、较低的成本,对环境相对友好,耐碱腐蚀等优势而引起研究人员的广泛关注。其中,金属硫化物中硫钴镍是一种典型的双金属硫化物。硫钴镍具有理论容量高、电负性较低、电化学活性高、资源丰富易得、无毒、易制备等特点,因此被广泛用于超级电容器的电极材料。硫钴镍虽然具有较高的理论容量,但目前仍面临以下几个严重问题:(1)硫钴镍导电性差,实际电化学比容量低于理论容量;(2)硫钴镍在充放电过程中存在严重的体积膨胀,使得电容器结构被破坏进而造成电容器循环性能的快速衰减。目前的解决办法一般是通过将硫钴镍与各种碳材料、金属氧化物及导电聚合物复合,改善材料的结构、形貌和导电性,以此提高材料的电化学性能。硫钴镍与金属氧化物、硫钴镍与碳材料复合的电极材料在制成超级电容器的电极极片时需要添加导电剂和粘结剂,这不仅增加了电极的成本,而且也使制作环节变得复杂,更重要的是活性物质的外露面积也会因为粘结剂的使用而减小。现在许多研究将导电活性物质直接生长在集流体上形成自支撑结构,这种结构形式既简化了超级电容器电极的制作流程,又提高了电容器的电化学性能。本研究以Ti片为基底,采用分步水热法先在Ti片表面生长TiO2纳米带阵列,然后在其上包覆生长NiCo2S4纳米片,得到NiCo2S4纳米片包覆TiO2纳米带的核/壳阵列结构。将TiO2@NiCo2S4作为超级电容器无粘结剂和导电剂的电极。三电极测试结果表明:1 A·g-1时TiO2@NiCo2S4电极的比电容达到1 300 F·g-1。此外,将煤基多孔碳(CPC)作为负极,TiO2@NiCo2S4作为正极,组装成了TiO2@NiCo2S4//煤基多孔碳(CPC)不对称超级电容器(ASC)。电化学测试结果表明:TiO2@NiCo2S4//CPC不仅具有较高的能量密度和功率密度(在400 W·kg-1时为41.6 Wh·kg-1),而且具有良好的循环稳定性(在4 A·g-1下循环5 000次后,电容保持率大于80%)。这是由于采用多级阵列式结构的复合电极具有以下优势:(1)比表面积大,增大了活性物质和电解液的接触面积;(2)孔道丰富,减少了电解液离子迁移的距离;(3)避免了使用传统电极制作过程中导电剂和粘结剂,减少了生产成本、缩短了加工时间。这种交织的三维(3D)网络结构和柔性衬底的设计为获得高性能柔性衬底电极材料提供了新方法。

Wearable electronic devices have attracted significant attention owing to their very high portability.However,the implementation of these electronic devices places high requirements on corresponding power supply systems,such as light weight,high flexibility,high energy and power densities.We attempt to use metal foil as electrodes for flexibility supercapacitors(SCs),which offer unique properties such as high mechanical strength and high electrochemical capacitance.Nowadays,Highly ordered TiO2 nanobelts@NiCo2 S4 nanoplates core/shell arrays on the Ti foil substrate(TiO2@NiCo2 S4) have been controllable fabricated via a stepwise hydrothermal approach and further investigated as additive-free anode materials for SCs exhibit a positive synergistic effect and display high capacity,good rate capacity and excellent cycle stability.The unique structure not only greatly promotes the transmission of electrons and charges,but also effectively reduces the volume expansion in redox reaction,and has good electrochemical performance in terms of specific capacitance and rate capability.Furthermore,the asymmetric supercapacitors based on TiO2@NiCo2 S4//coal-based porous carbon electrodes demonstrate a high energy density(41.6 Wh·kg-1 at400 W·kg-1).To verify the feasibility of TiO2@NiCo2 S4//CPC capacitors for energy supply,a two-series battery was assembled to drive the green LED.The device can power the LED for 10 minutes.The design of this interwoven three-dimensional(3 D) frame architecture and flexible substrate opens up new opportunities to obtain high comprehensive performance flexible substrate electrode materials in the energy storage field.