L.Y. Yang

Self-Assembly of Parallelly Aligned NiO Hierarchical Nanostructures with Ultrathin Nanosheet Subunits for Electrochemical Supercapacitor Applications

Parallelly aligned NiO hierarchical nanostructures were fabricated using a templated self-assembly method followed by calcinations, where rationally employed pluronic triblock copolymers (P123) are acting as molecular templates for geometrical manipulation of nanocrystals and short-chain alcohols are acting as cosolvents and cosurfactants. Such aligned nanostructure is constructed orderly with several ultrathin two-dimensional (2D) nanosheet subunits with an exceptionally small thickness of only 3 nm in a high degree of orientation and separation. Moreover, the number of assembled nanosheets in a unit can be tuned by changing the concentration of the involving P123. This is the first time to synthesize highly hierarchically ordered and bilaterally symmetrical nanostructures, distributed in diameter of around 200-300 nm, via self-assembly in the liquid phase without solid substrates. The as-synthesized NiO delivered high capacitances of 418 F/g at the current density of 2 A/g with well cycling stability (still maintained 85% after 2000 cycles) and 333 F/g at 10 A/g in rates performance after 60 cycles. These fine electrochemical performances are supposed to be attributed to the hierarchical structures with high specific surface area (SSA, ∼164.87 m(2)/g) and ordered multilevel mesopores, which facilitate the electrolyte accessibility and provide more active sites for redox reaction.

Yolk–Shell Sn@C Eggette-like Nanostructure: Application in Lithium-Ion and Sodium-Ion Batteries

Yolk-shell carbon encapsulated tin (Sn@C) eggette-like compounds (SCE) have been synthesized by a facile method. The SCE structures consist of tin cores covered by carbon membrane networks with extra voids between the carbon shell and tin cores. The novel nanoarchitectures exhibit high electrochemical performance in both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). As anodes for LIBs, the SCE electrodes exhibit a specific capacity of ∼850 mA h g(-1) at 0.1 C (100 mA g(-1)) and high rate capability (∼450 mA h g(-1) remains) at high current densities up to 5 C (5000 mA g(-1)). For SIBs, the SCE electrodes show a specific capacity of ∼400 mA h g(-1) at 0.1 C and high rate capacity (∼150 mA h g(-1) remains) at high current densities up to 5 C (5000 mA g(-1)).

Facile Synthesis of Na0.33V2O5 Nanosheet-Graphene Hybrids as Ultrahigh Performance Cathode Materials for Lithium Ion Batteries

Na0.33V2O5 nanosheet-graphene hybrids were successfully fabricated for the first time via a two-step route involving a novel hydrothermal method and a freeze-drying technique. Uniform Na0.33V2O5 nanosheets with a thickness of about 30 nm are well-dispersed between graphene layers. The special sandwich-like nanostructures endow the hybrids with high discharge capacity, good cycling stability, and superior rate performance as cathodes for lithium storage. Desirable discharge capacities of 313, 232, 159, and 108 mA·h·g(-1) can be delivered at 0.3, 3, 6, and 9 A·g(-1), respectively. Moreover, the Na0.33V2O5-graphene hybrids can maintain a high discharge capacity of 199 mA·h·g(-1) after 400 cycles even at an extremely high current density of 4.5 A·g(-1), with an average fading rate of 0.03% per cycle.

Carbon fiber cloth@VO2 (B): excellent binder-free flexible electrodes with ultrahigh mass-loading

Flexible batteries have attracted much attention in recent years due to their promising applications in flexible displays, portable consumer electronic devices, and thin-film-based electronics. However, their practical applications are still limited by their low active material mass-loading in flexible electrodes and poor lithium storage performances. In this work, we have successfully grown highly crystalline VO2 nanobelt arrays on carbon fiber cloth (CFC) for the first time. The strategy only involves a facile one-pot solvothermal method. As binder-free flexible electrodes for LIBs, even with active material mass loading dramatically reaching up to 5.2 mg per square centimeter, such a novel CFC@VO2 (B) nanobelt array cathode electrode still exhibits a specific capacity of 145 mA h g−1 (90% of theoretical capacity), excellent cyclability with capacity retention over 90% after 200 cycles at ∼9C (1000 mA g−1), and high rate capability at high current densities up to ∼20C (2000 mA g−1). Such an excellent cathode material is very desirable in high-power flexible LIBs. The effective combination of CFC and a high areal mass loading of active materials described in this paper is a feasible and effective solution to design high-performance flexible batteries, especially high-power flexible batteries.