Porous Poly(Poly[Ethylene Glycol] Methyl Ether Methacrylate) Gel Polymer Electrolyte With Superior Electrochemical Properties in a High-Performance Potassium-Ion Battery

Potassium-ion batteries as a suitable alternative to lithium-ion batteries have drawn attention due to available sources of potassium, low reduction potential, better diffusion through electrolyte/electrode interface, and good ionic conductivity. Here, a photopolymerized porous gel polymer electrolyte based on poly(poly[ethylene glycol] methyl ether methacrylate) and poly(methyl methacrylate) nanoparticles shows superior thermal and electrochemical properties. After swelling in a KPF₆ and EC/PC solution, the best GPE demonstrates high ionic conductivity of 2.9 × 10⁻² S cm⁻¹, potassium transference number of 0.88, and high electrochemical stability of > 6 V. This excellent electrochemical property could be related to high solvent uptake, high surface area, K⁺ pathway channels, low T_g, and the electron donor groups of the porous poly(poly[ethylene glycol] methyl ether methacrylate). Also, this GPE shows an initial capacity of 155 mAh g⁻¹, an initial Coulombic efficiency of ~100%, and capacity retention of 99.9% after 100 cycles in a high current density of 5 C with high-voltage FeFe(CN)₆ as the cathode and graphite as the anode. FE-SEM images show the ability to suppress dendrites after 100 cycles of charge–discharge at 5 C. Additionally, this GPE demonstrates 143 mAh g⁻¹ capacity at a very high C-rate of 10, showing its ability for use in high-performing rechargeable potassium batteries.