This dataset provides the raw data to the manuscript "From lithium to potassium: Comparison of cations in poly(ethylene oxide)-based block copolymer electrolytes for solid-state alkali metal batteries" published in Electrochimica Acta, Vol. 454, 20 June 2023. https://doi.org/10.1016/j.electacta.2023.142421 Specifically, the following measurements are provided: Solid polymer electrolytes characterization: Differential Scanning Calorimetry ("DSC_") Rheological measurements ("RHEO_") Electrochemical Impedance Spectroscopy ("EIS_") Transference Number Measurements: Bruce-Vincent Method ("T+_EIS_ & T+_CA_") Pulsed Field Gradient NMR ("PFG_NMR_") Plating and Stripping Experiments ("PlatingStripping_") Prussian Blue analogue (PBA) characterization: Thermogravimetric analysis ("TGA_") Electrochemical cell tests of liquid and solid polymer electrolytes ("CYCLING_")