Anti-liquid metal permeation separator for stretchable potassium metal batteries

Non-Newtonian fluid state Na-K (NaK) electrodes (NNFS-NaK) have strong adhesion and permeability during the continuous charging and discharging process, which has been raised in our previous work. After three years of exploration, the nano-Ag-based anti-permeation film is designed to solve this issue. DFT theoretical calculation results between NaK and Ag show alloying resistance at room temperature to keep the stability of the anti-permeation film. And in both symmetric and complete cells, the cells with nano-Ag-based lubrication film (AgLF) on the Whatman separator (AgLF/Whatman separator) have a lower overpotential, higher specific capacity, and Coulomb efficiency. When a flexible stretchable device is under stretching, folding, and bending, nano-Ag adhered to the surface of NNFS-NaK will slip with the nano-Ag on the separator to avoid the NaK infiltration. As a result, the assembled cells and full batteries equipped with anti-permeation films have better cycling stability. This discovery promotes the broader application of dendrite-free alkali metal batteries.