Abstract
Vanadium bronzes have been well-demonstrated as promising cathode materials for aqueous zinc-ion batteries. However, conventional single-ion pre-intercalated V2O5 nearly reached its energy/power ceiling due to the nature of micro/electronic structures and unfavourable phase transition during Zn2+ storage processes. Here, a simple and universal in-situ anodic oxidation method of quasi-layered CaV4O9 in a tailored electrolyte was developed to introduce dual ions (Ca2+ and Zn2+) into bilayer δ-V2O5 frameworks forming crystallographic ultra-thin vanadium bronzes, Ca0.12Zn0.12V2O5·nH2O. The materials deliver transcendental maximum energy and power densities of 366 W h kg−1 (478 mA h g−1 @ 0.2 A g−1) and 6627 W kg−1 (245 mA h g−1 @ 10 A g−1), respectively, and the long cycling stability with a high specific capacity up to 205 mA h g−1 after 3000 cycles at 10 A g−1. The synergistic contributions of dual ions and Ca2+ electrolyte additives on battery performances were systematically investigated by multiple in-/ex-situ characterisations to reveal reversible structural/chemical evolutions and enhanced electrochemical kinetics, highlighting the significance of electrolyte-governed conversion reaction process. Through the computational approach, reinforced “pillar” effects, charge screening effects and regulated electronic structures derived from pre-intercalated dual ions were elucidated for contributing to boosted charge storage properties.
Highlights
The burgeoning energy market is hastening the development of electrochemical energy in terms of safety, eco-friendliness and economic sustainability [1]
aqueous zinc-ion batteries (AZIBs) are still suffering from underdeveloped cathode materials because of sluggish kinetics related with the strong electrostatic interaction between divalent species (i.e., Zn2+ and hydrated Zn2+) and the host framework [10]
Structural collapse/dissolution, irreversible phase transformation and poor electronic conductivity of cathode materials are concretely responsible for unsatisfactory cycling stability and relatively low specific capacity (
Summary
The burgeoning energy market is hastening the development of electrochemical energy in terms of safety, eco-friendliness and economic sustainability [1]. The battery with Ca(CF3SO3)2 as the electrolyte additive possesses smaller potential differences between the two pairs of anodic and cathodic peaks, respectively, along with relatively large specific currents at each potential compared with those in pure Zn(CF3SO3)2 electrolyte, which indicates less polarisation (e.g., better diffusion kinetics) and higher capacity upon fast scan rates.
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