Defect-Rich MoO₃ Nanobelt Cathode for a High-Performance Hybrid Alkali/Acid Zn-MoO₃ Rechargeable Battery

Abstract

Protons (H+) and hydroxide ions (OH–) are regarded as ideal charge carriers for rechargeable batteries thanks to their small size, high ion mobility, low cost, and wide flexibility compared to the metal ions. However, the implementation of storage of both H+ and OH– in one electrochemical energy device faces grand challenges due to incompatibility between H+ and OH–. Herein, we report an alkali-acid Zn-MoO3 hybrid battery that employs H+ and OH– as charge carriers of the cathode and anode, respectively, in which the insertion/deinsertion of H+ take place on the defect-rich MoO3 porous nanobelt (d-MoO3 PNB) cathode in acid while OH– are involved in the alkaline conversion of Zn anode, which offers a promising route to better address the incompatible issues of H+ and OH– in one system. The d-MoO3 PNB with abundant oxygen vacancies holds more favorable properties for H+ storage than the MoO3 NB, as verified by the fact that the former can deliver significantly enhanced capacity and robust stability relative to the latter. The density functional theory (DFT) calculations demonstrate that the d-MoO3 can lower the barrier for H+ storage with improved conductivity, which is beneficial for improving the electrochemical performance. As a result, the alkali-acid Zn-MoO3 hybrid battery can deliver a high open-circuit voltage of 1.85 V, a high rate capability of 158 mAh g–1 at a current density of 5 A g–1, and excellent capacity retention of above 90% over 200 cycles. This work sheds light on the development of aqueous energy devices with high voltage and energy density through materials engineering and device optimization.

Aqueous OH−/H+ Dual‐Ion Zn‐Based Batteries

“…cathode in acid (Figure 5g). [22] Both electrodes show redox activity at their individual potential windows from the CV curves (Figure 5h), indicating the availability and feasibility of fabricating an alkaline-acidic dual-ion ZnÀ MoO 3 battery. Zn would be oxidized to Zn(OH) 4 2À with consumption of OH À on the anode and MoO 3 would be reduced H x MoO 3 with consumption of H + on the cathode during the discharging process, while H + and OH À would be generated on the cathode and anode, respectively during the charging process.…”

Design Strategies and Recent Advancements for Low‐Temperature Aqueous Rechargeable Energy Storage

“…Controllably constructing defects in electrodes can fundamentally increase their electrical conductivity, accelerate ions diffusion and charges transfer, decrease the stress and electrostatic repelling forces between adjacent layers, and directly overcome migration and diffusion obstacles. [141][142][143] On the other hand, introducing defects can provide sufficient active sites for ions or intermediates adsorption and reaction, which is beneficial for maintaining their structural stability and flexibility. Galvanostatic intermittent titration results revealed that the ammonium vanadate cathode with oxygen-defect had a satisfied Zn 2+ diffusion coefficient of ≈10 −9 cm 2 s −1 under −30 °C (Figure 12f,g), because the deficient oxygen atoms in bilayered structure distinctly decreased the zinc diffusion energy barrier and improved its structural stability, delivering a cyclic stability of 2600 cycles life at 2 A g −1 under −30 °C.…”

Charge Carriers for Aqueous Dual‐Ion Batteries

“…[52] An H + DIB with OH À as the anion carrier has been assembled using a device containing cathode and anode chambers separated by Nafion membrane that allows only proton to pass through. [54] Defect-rich MoO 3 porous nanobelt is applied as cathode in electrolyte of 2 m H 2 SO 4 solution, and zinc is applied as anode in alkali electrolytes containing 4 m NaOH and 0.1 m Zn(CH 3 COO) 2 solution. The intercalation/de-intercalation of H + takes place in the cathode side by Equation (2):…”