Interlayer Engineering of α‐MoO₃ Modulates Selective Hydronium Intercalation in Neutral Aqueous Electrolyte

Abstract

Among various charge-carrier ions for aqueous batteries, non-metal hydronium (H₃ O⁺ ) with small ionic size and fast diffusion kinetics empowers H₃ O⁺ -intercalation electrodes with high rate performance and fast-charging capability. However, pure H₃ O⁺ charge carriers for inorganic electrode materials have only been observed in corrosive acidic electrolytes, rather than in mild neutral electrolytes. Herein, we report how selective H₃ O⁺ intercalation in a neutral ZnCl₂ electrolyte can be achieved for water-proton co-intercalated α-MoO₃ (denoted WP-MoO₃ ). H₂ O molecules located between MoO₃ interlayers block Zn²⁺ intercalation pathways while allowing smooth H₃ O⁺ intercalation/diffusion through a Grotthuss proton-conduction mechanism. Compared to α-MoO₃ with a Zn²⁺ -intercalation mechanism, WP-MoO₃ delivers the substantially enhanced specific capacity (356.8 vs. 184.0 mA h g^-1 ), rate capability (77.5 % vs. 42.2 % from 0.4 to 4.8 A g^-1 ), and cycling stability (83 % vs. 13 % over 1000 cycles). This work demonstrates the possibility of modulating electrochemical intercalating ions by interlayer engineering, to construct high-rate and long-life electrodes for aqueous batteries.