Alloying-type materials are promising anodes for high-performance sodium-ion batteries (SIBs) because of their high capacities and low Na-ion insertion potentials. However, the typical candidates, such as P, Sn, Sb, and Pb, suffer from severe volume changes (≈293-487%) during the electrochemical reactions, leading to inferior cycling performances. Here, a high-rate and ultrastable alloying-type anode based on the rolled-up amorphous Si nanomembranes is demonstrated. The rolled-up amorphous Si nanomembranes show a very small volume change during the sodiation/desodiation processes and deliver an excellent rate capability and ultralong cycle life up to 2000 cycles with 85% capacity retention. The structural evolution and pseudocapacitance contribution are investigated by using the ex situ characterization techniques combined with kinetics analysis. Furthermore, the mechanism of efficient sodium-ion storage in amorphous Si is kinetically analyzed through an illustrative atomic structure with dangling bonds, offering a new perspective on understanding the sodium storage behavior. These results suggest that nanostructured amorphous Si is a promising anode material for high-performance SIBs.
HIGHLIGHTS • Divalent magnesium ions as electrolyte additives are first used to improve the performance of vanadium-based cathodes for aqueous ZIBs. • Pre-adding magnesium ions into electrolytes provide an appropriate equilibrium balance between the dissolution and recombination of magnesium vanadates, thus suppress the continuous dissolution of active materials, and lead to a higher stability of the electrode. • The hybrid aqueous electrolytes with cost-effective ZnSO 4 and MgSO 4 salts show a better competitive prospective for the stationary grid-scale applications.
Creating oxygen vacancies to tune the surface electronic structure is a feasible approach to enhance the electrocatalytic activities of noble-metal-free transition-metal oxides for Li−O 2 batteries. Herein, vacancy-rich Co 3 O 4 hollow porous nanospheres have been obtained through a facile reduction strategy from Co 3 O 4 hollow porous nanospheres, which were prepared in a self-template construction manner through a solvothermal synthesis followed by a heat treatment. The reduced Co 3 O 4 hollow porous nanospheres composed of numerous nanoparticles show a unique porous and hollow structure with abundant surface oxygen vacancies. The oxygen vacancy defects can produce more electrochemical active sites and improve the electrical conductivity as well as increase the adsorbed oxygen-containing molecules for the enhanced Li−O 2 battery performance. Therefore, the reduced Co 3 O 4 sample with oxygen vacancies shows lower overpotential, higher discharge capacity, longer cycling life, and better rate capability than the pristine one. KEYWORDS: Li−O 2 batteries, oxygen vacancies, defects, Co 3 O 4 , hollow, spheres
The yolk–shell structure, realized by various synthesis methods, exhibits unique morphology and structural properties, which is currently undergoing a transition from material production technology to energy storage applications.
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