Interlayer Engineering of α‐MoO(3) Modulates Selective Hydronium Intercalation in Neutral Aqueous Electrolyte

Among various charge‐carrier ions for aqueous batteries, non‐metal hydronium (H(3)O(+)) with small ionic size and fast diffusion kinetics empowers H(3)O(+)‐intercalation electrodes with high rate performance and fast‐charging capability. However, pure H(3)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 H(3)O(+) intercalation in a neutral ZnCl(2) electrolyte can be achieved for water‐proton co‐intercalated α‐MoO(3) (denoted WP‐MoO(3)). H(2)O molecules located between MoO(3) interlayers block Zn(2+) intercalation pathways while allowing smooth H(3)O(+) intercalation/diffusion through a Grotthuss proton‐conduction mechanism. Compared to α‐MoO(3) with a Zn(2+)‐intercalation mechanism, WP‐MoO(3) 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.