An effective, nondestructive, and universal strategy to homogeneously modify freestanding carbon nanotube (CNT) films with various active species is essential to achieve functional electrodes for flexible electrochemical energy storage, which is challenging and has attracted considerable research interest. In this work, a generalizable concept, to utilize silicon oxide as the intermediate to uniformly decorate various metal sulfide nanostructures throughout CNT films is reported. Taking nickel sulfide nanosheet/CNT (NS/CNT) films, in which the NS nanosheets are homogeneously attached on the intact few‐walled CNTs, as an example, the sheet‐like NS provides sufficient active sites for redox reactions and the CNT network acts as an efficient electron highway, maintaining the structural integrity of the composite and also buffering volume changes. These merits enable NS/CNT films to meet the requirements of versatile energy storage applications. When used for supercapacitors, a high specific capacitance (2699.7 F g−1/10 A g−1), outstanding rate performance at extremely high rates (1527 F g−1/250 A g−1), remarkable cycling stability, and excellent flexibility can be achieved, among the best performance so far. Moreover, it also delivers excellent performance in the storage of Li and Na ions, meaning it is also potentially suitable for Li/Na ion batteries.
Boron-doped carbon nanotubes are a promising candidate for Li storage due to the unique electronic structure and high crystallinity brought by the boron dopants. However, the relatively low Li storage capacity has limited its application in the electrochemical energy storage field, which is mainly caused by the predominantly intact graphitic structure on their surface with limited access points for Li ion entering. Herein, we report a novel B-doped CNTs (py-B-CNTs) film, in which the CNTs possess intrinsically rough surface but flat internal graphitic structure. When used as a flexible anode material for LIBs, this py-B-CNTs film delivers significantly enhanced capacity than the conventional B-doped CNTs or the pristine CNTs films, with good rate capability and excellent cycling performance as well. Moreover, this flexible film also possesses excellent mechanical flexibility, making it capable of being used in a prototype flexible LIB with stable power output upon various bending states.
Carbon nanotubes (CNTs) are an excellent electrode material for capacitive deionization (CDI), due to their excellent electronic conductivity and outstanding chemical/physical stability. Their powder form and easy aggregation, however, have greatly limited their practical CDI performance. Aiming to address this issue, the authors report a freestanding CNT film which was fabricated by floating-catalyst chemical vapor deposition, as a binder-free electrode for CDI. By simply adjusting the pyrrole content in the precursor, the morphology of the resulting CNT film can be tuned to meet the requirements of CDI. In the presence of 2 wt.% pyrrole, the CNT film with a mesoporous structure exhibited a large specific surface area of 198 m2/g and an increased electric double-layer capacity (40 F/g), which is more than two times as large as that of the pristine CNT film. Due to these merits, the electrosorption capacity for sodium chloride (NaCl) of the CNT film electrode (11·39 mg/g) has been greatly improved compared with that of the pristine CNT film (4·52 mg/g), showing a good potential for large-scale practical CDI.
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