Dynamic Regulation Achieving High-Performance La-Containing Prussian Blue Analogues for Aqueous K + Storage.

Lanthanum (La), an "industrial aginomoto" element, exhibits that a small amount of introduction would greatly improve performance. However, La-containing Prussian blue analogues (PBAs) would be dissolved into aqueous solutions, which cannot act as a potassium-ion (K + ) storage host. Here, an effective dynamic regulating strategy (chemical components and structures) is developed to overcome the high solubility of La-containing PBA in aqueous electrolytes and achieve high structural stability and superior aqueous K + storage. For chemical component regulation, Fe 3+ ions in the electrolyte fill the La 3+ vacancies on the surface and the modified surface hinders the La atoms from further dissolving, and the remaining La atoms in bulk phase improve electron/ion transfer ability and amount of K + storage. For the structure regulation, the material is transferred from the hexagon to the cubic lattice during charging-discharging procedures, achieving a highly thermodynamically optimal structure. The cathode presents ultrahigh capacities of 171, 155, 132, and 116 at current densities of 1, 2, 3, and 4 A g -1 respectively, and the capacity remains almost constant after 1000 cycles. The mechanism is revealed by experiments and density functional theory (DFT).