ABSTRACT
We demonstrated the use of hydrated calcium vanadate (CaV6O16·3H2O, denoted as CaVO-2) as a cathode for aqueous zinc-ion batteries (AZIBs). Nanoribbons of hydrated calcium vanadate facilitated shortening of the Zn2+ transport distance and accelerated zinc-ion insertion. The introduction of interlayer structure water increased the interlayer spacing of calcium vanadate and as a "lubricant". Ca2+ insertion also expanded the interlayer spacing and further stabilized the interlayer structure of vanadium-based oxide. The density functional theory results showed that the introduction of Ca2+ and structured water could effectively improve the diffusion kinetics, resulting in the rapid transport of zinc ions. As a result, AZIBs based on the CaVO-2 cathode offered high specific capacity (329.6 mAh g-1 at 200 mA g-1) and fast charge/discharge capability (147 mAh g-1 at 10 A g-1). Impressively, quasi-solid-state zinc-ion batteries based on the CaVO-2 cathode and polyacrylamide-cellulose nanofiber hydrogel electrolytes maintained an outstanding specific capacity and long cycle life (162 mAh g-1 over 10â¯000 cycles at 5 A g-1). This study provided a reliable strategy for metal-ion insertion and the structural water introduction of oxides to produce a high-quality cathode for ZIBs. Meanwhile, it provides ideas for the combination of vanadium-based materials and gel electrolytes to construct solid-state zinc-ion batteries.
ABSTRACT
Molybdenum sulfide has been widely investigated as a prospective anode material for Li+/Na+ storage because of its unique layered structure and high theoretical capacity. However, the enormous volume variation and poor conductivity limit the development of molybdenum sulfide. The rational design of a heterogeneous interface is of great importance to improve the structure stability and electrical conductivity of electrode materials. Herein, a high-temperature mixing method is implemented in the hydrothermal process to synthesize the hybrid structure of MoS2/V2O3@carbon-graphene (MoS2/V2O3@C-rGO). The MoS2/V2O3@C-rGO composites exhibit superior Li+/Na+ storage performance due to the construction of the interface between the MoS2 and V2O3 components and the introduction of carbon materials, delivering a prominent reversible capacity of 564 mAh g-1 at 1 A g-1 after 600 cycles for lithium-ion batteries and 376.3 mAh g-1 at 1 A g-1 after 450 cycles for sodium-ion batteries. Theoretical calculations confirm that the construction of the interface between the MoS2 and V2O3 components can accelerate the reaction kinetics and enhance the charge-ionic transport of molybdenum sulfide. The results illustrate that interfacial engineering may be an effective guide to obtain high-performance electrode materials for Li+/Na+ storage.
ABSTRACT
Ingenious morphology design and doping engineering have remarkable effects on enhancing conductivity and reducing volume expansion, which need to be improved by transition metal oxides serving as anode materials for lithium-ion batteries. Herein, S0.15-Fe2O3@C nano-spindles with a hierarchical porous structure are obtained by carbonizing MIL-88B@PDA and subsequent high-temperature S-doping. Kinetic analysis showed that S-doping increases capacitive contribution, enhances charge transfer capability and accelerates Li+ diffusion rate. Therefore, the S0.15-Fe2O3@C electrode exhibits superior lithium storage performance with a remarkable specific capacity of 1014.4 mA h g-1 at 200 mA g-1, ultrahigh rate capability of 513.1 mA h g-1 at 5.0 A g-1, and excellent cycling stability of 842.3 mA h g-1 at 1.0 A g-1 after 500 cycles. Moreover, the size of S0.15-Fe2O3@C particles barely changed after 50 cycles, indicating an extremely low volume expansion, related to the carbon shell, fine Fe2O3 nanoparticles, abundant voids inside, and improved kinetics. This strategy can be applied to other metal oxides for synthesizing anodes with high-rate capability and low volume expansion.