The effect of H2O in electrolytes and in electrode lattices on the thermodynamics and kinetics of reversible multivalent‐ion intercalation chemistry based on a model platform of layered VOPO4 has been investigated. The presence of H2O at the electrolyte/electrode interface plays a key role in assisting Zn2+ diffusion from electrolyte to the surface, while H2O in the lattice structure alters the working potential. More importantly, a dynamic equilibrium between bulk electrode and electrolyte is eventually reached for H2O transport during the charge/discharge cycles, with the water activity serving as the key parameter determining the direction of water movement and the cycling stability. Water of life: H2O at the electrolyte/electrode interface plays a key role in assisting Zn2+ diffusion from electrolytes to the bulk surface, while H2O in the lattice structure alters the working potential. A dynamic equilibrium between the bulk electrode and electrolyte is eventually established for H2O transport during the charge/discharge cycles.