In situ construction of ball-in-ball structured porous vanadium pentoxide intertwined with carbon fibers induces superior electronic/ionic transport dynamics for aqueous zinc-ion batteries

Hypothesis Using V 2 O 5 as an aqueous zinc-ion battery (ZIB) cathode has major drawbacks, including inferior electrode/electrolyte contact interfaces, morphological and structural deterioration, and unsatisfactory conductivity. Purposeful construction of ball-in-ball structured V 2 O 5 with porous and void architectures wrapped with carbon fibers is expected to overcome the drawbacks, thus bringing the electrochemical performance of V 2 O 5 into full play. Experiments In situ construction of ball-in-ball structured porous V 2 O 5 wrapped by intertwined carbon fibers (V 2 O 5 @void@V 2 O 5 @CFs) is implemented through a simple combined hydrothermal and calcination route. A combination of in/ex situ analytical methods and density functional theoretical calculations are performed to clarify the energy storage mechanism of the material for aqueous ZIBs. Findings The reversible reaction to generate Zn x V 2 O 5 ·nH 2 O executes during the zinc ion insertion/extraction procedure in V 2 O 5 @void@V 2 O 5 @CFs. Benefitting from the synergistic effect of the porous ball-in-ball structure with void space and the wrapped CFs, the material exhibits boosted specific capacity (455 mAh g −1 after 100 cycles and 149 mAh g −1 after 2000 cycles at 4 and 25 A g −1 , respectively), cyclic stability, rate ability and energy density (355 Wh kg −1 at 739 W kg −1 ) when used for aqueous ZIBs due to improved capacitive contribution, fast zinc ion transport dynamics, and enhanced conductivity.