Structural engineering of hydrated vanadium oxide cathode by K+ incorporation for high-capacity and long-cycling aqueous zinc ion batteries

Enabling stable MnO2 matrix for aqueous zinc-ion battery cathodes

“…Among the candidates, vanadium-based cathodes exhibit the highest specic capacity (>300 mA h g À1 ) and prolonged cyclability, but their working voltage window is relatively low (<1.0 V vs. Zn/Zn 2+ ), which hinders their practical use for high energy density applications. [13][14][15][16][17] Prussian blue analogs (PBAs) operate at a high working voltage (1.5-1.7 V vs. Zn/Zn 2+ ) but suffer from the relatively low specic capacity (50-120 mA h g À1 ). 18,19 Manganese-based cathodes not only share outstanding specic capacity (200-300 mA h g À1 ) and high working voltage range (1.3-1.35 V vs. Zn/Zn 2+ ) [20][21][22][23][24] but also exhibit the advantages of abundant reserves, simple fabrication, low cost and environmental friendliness, and have therefore become a research hotspot.…”

Interlayer Doping in Layered Vanadium Oxides for Low‐cost Energy Storage: Sodium‐ion Batteries and Aqueous Zinc‐ion Batteries

“…Thus, Tian et al. achieved both the high specific capacity and long‐life cyclic stability by pre‐intercalating the K + with the lowest electronegativity of 0.82 [80] . From another perspective, the strong electrostatic interaction of Al 3+ , which has high electronegativity (1.61) though, can be tightly bound with the surrounding lattice, achieving the improved stability as well (Figure 6d) [85] .…”

“…Generally, the interlayered metal cations pre‐intercalation is always accompanied by the co‐doping of water molecules especially in AZIBs. Similar to the pre‐intercalation of water molecules, the structural water here also acts as an electrostatic shield for Zn 2+ , broadens the diffusion tunnels, and alters the working potential, which can reduce electrostatic bond strength and enhance Zn 2+ intercalation kinetics [9,79,80] . As for the difference in electrochemical performance of ion and molecular pre‐intercalation layers, it is mainly determined by the diversity of intercalated metal ions.…”

“…where X a and X b are the electronegativity of anion and cation, respectively. Compared to V−O bond, M−O bond (M is the main group metal elements) has a higher ionic character value and binding energy due to the lower electronegativity, [80,87] which means the stronger interaction between the layers and more stable crystal structure. Thus, Tian et al.…”

“…For example, Tian et al. exhibited the narrower d‐spacing from 12.0 to 9.9 Å after pre‐intercalating K + in hydrated vanadium oxide, but the ion diffusion is significantly enhanced [80] . This could be attributed to the oxygen vacancies induced by K + incorporation, which motivates electron hoping between V 4+ /V 5+ to improve the conductivity.…”