UV-cured gel polymer electrolyte for stable potassium-batteries

Efficient energy storage systems will play a pivotal role in the energetic transition we are facing. In particular, batteries are fundamental electrochemical storage systems that can store directly the intermittent energy produced by renewable sources. Nowadays, the most know batteries are based on lithium and display high energy density and lightness. However, the uneven distribution of lithium in the Earth crust threatens their further development on a large scale. Consequently, the research moved toward post-lithium technologies, such as potassium-ion systems. A fundamental component in batteries is the electrolyte, which has the role to compensate the charge. For practical application, the electrolyte should ensure stability and charge mobility, as well as safety. In this regard, solid and quasi-solid systems can prevent solvent evaporation and leakage, but, on the other end, usually present low ionic conductivity. Herein, we present the first photocured gel polymer electrolyte (GPE) for potassium batteries. UV-curing is a rapid and low energy-demanding process for the synthesis of polymers and does not require further purification steps. The GPE obtained by the radical polymerization of acrylate and methacrylate monomers displayed a high ionic conductivity (17 mS cm-1) and wide electrochemical stability window (up to 3.7 V vs. K+/K). The thermal resistance is suitable for potassium batteries and the glass transition temperature is low enough to ensure a good macromolecular mobility of the polymer chains. The GPE provided mechanical stability and was able to hinder the formation of potassium dendrites. All these features allowed the unprecedent achievement of 600 cycles with a capacity retention of 58%.