Nanotubes for Energy Storage
Nanotubes (NTs) are promising candidates as energy storage materials for hydrogen, electricity, and lithium because of their unique structural, mechanical, and electrical properties. The performance of NT-based energy storage materials is considerably improved compared to the conventional bulk-based materials. In addition, the open structure of NTs can help to improve the storage capacity. In this review, we systematically discuss the applications of NTs in energy storage, and the influence of their structures and morphologies on their performance for hydrogen storage, supercapacitor, and lithium battery. We show that the modification of NTs (functionalization, doping, defect control, and structure engineering) and the design of NT-based composite structures (hybrid and ternary composites including NTs, graphene, oxides, polymers, and metal) provide strategies to improve the performance of NT-based energy storage materials.