Silver vanadium oxide@water-pillared vanadium oxide coaxial nanocables for superior zinc ion storage properties

Abstract

Effective ionic/electronic percolation, especially in a thick electrode, has a decisive influence on the electrochemical properties of rechargeable batteries, such as material usefulness, electrode reversibility and cell lifespan. Using low cost and highly safe rechargeable aqueous zinc ion batteries (RAZBs) as a model, in this paper a dense electrode architecture is presented which is constructed using silver vanadium oxide@water-pillared vanadium oxide core–shell (Ag_0.333V₂O₅@V₂O₅·nH₂O) coaxial nanocables that maintain optimal ion/electron percolation without admixing the additional inert component. This electrochemically robust architecture is composed of a highly electronic conductive phase of silver vanadate and a highly ionic conductive phase of the water-pillared V₂O₅·nH₂O structure, which synergistically forms a coaxial nanocable structure benefiting ion/electron contact and penetration in a thick electrode. As expected, the Ag_0.333V₂O₅@V₂O₅·nH₂O coaxial nanocables deliver a high reversible capacity (312.1 mA h g⁻¹ at 0.5 A g⁻¹), excellent rate capability (196.7 mA h g⁻¹ at 3.0 A g⁻¹) and stable cycling performance (261.7 mA h g⁻¹ at 0.5 A g⁻¹ after 100 cycles). The investigation of the electrochemical reaction kinetics reveals a combinatorial fast pseudocapacitive reaction and a diffusion controlled intercalation reaction. The lower percolation threshold of both ions and electrons should be responsible for the better electrode kinetics and the improved zinc ion storage capacity of the Ag_0.333V₂O₅@V₂O₅·nH₂O coaxial nanocables compared to that of pristine Ag_0.333V₂O₅ electrodes. It is anticipated that the as-proposed strategy of constructing effective ionic/electronic percolating thick electrodes to boost the reaction kinetics can be applied to other active materials for constructing practical multivalent batteries.