Recent advances in micro-/nano-structured hollow spheres for energy applications: From simple to complex systems

Abstract

Hollow micro-/nano-structured materials are now playing an important role in cutting edge innovations for energy conversion and storage technologies such as solar cells, fuel cells, lithium ion batteries and super capacitors. These materials show great promise in addressing growing environmental concerns for cleaner power sources at a time of increasing global demand for energy. In this perspective, we show that complex multi-shelled micro-/nano-materials show significant material advantages in many applications over conventional simple hollow structures. We also summarize the vast array of synthetic strategies used to create multi-shelled hollow structures, and discuss the possible application of these novel materials for power generation and storage. Finally, the emergent challenges and future developments of multi-shelled hollow structures are further discussed.

Graphene-modified nanostructured vanadium pentoxide hybrids with extraordinary electrochemical performance for Li-ion batteries

“…In addition, the AC impedance proves that the electric conductivity, the vanadium redox reaction and the Li þ diffusion have been improved due to the introduction of such a small amount of graphene. The performance of electrode materials is always rooted in the materials structure 58,59 . The graphene sheets sandwiched in between the V 2 O 5 layers not only enhance the electron conduction between the V 2 O 5 layers (intraparticle conduction, supported by TEM and XRD results) and between the V 2 O 5 ribbons (inter-particles conduction, supported by Cryo-TEM results), but also preserve the water molecules between the two layers of V 2 O 5 , which facilitates the Li þ diffusion (as can be seen from the AC impedance results).…”

Contribution of multiple reflections to light utilization efficiency of submicron hollow TiO2 photocatalyst

“…For applications in environmental and energy-related systems, various hollow spheres of metal, metal oxide, and carbon-based materials have been used in dye-sensitized solar cells [8], photocatalysis [9], fuel cells [10], lithium ion batteries [11], and supercapacitors [12]. It has been proven that the unique structure of hollow spheres provides an enhanced surface-to-volume ratio and reduced transport lengths for both mass and charge transport [13]. Particular interests have been attracted to the synthesis of hollow structures of TiO2, one of the most widely studied semiconducting oxide materials, and their applications in solar energy conversion [14].…”

High-rate lithiation-induced reactivation of mesoporous hollow spheres for long-lived lithium-ion batteries

“…Hierarchically meso-and nanoporous hollow spheres are recognized as promising electrode materials for electrochemical energy storages [19][20][21][22][23][24] , and the unique structure provides an enhanced surface-to-volume ratio and reduced lengths for both mass and charge transports. The hollow sphere also provides extra space to mitigate volume expansion/extraction, thus displaying enhanced cycling stabilities, particularly at low current densities.…”