My research activity with kalium

Potassium-ion batteries (PIBs) are one of the top candidates to replace Li-ion batteries for stationary applications. Li-ion batteries (LIBs) have reached unprecedent targets of performance and safety, which ensure the Li-ion system as the best choice for portable divices and electric vehicles. Nevertheless, as lithium is now in the list of critical raw materials due to its low abundancy (0.0017 wt% in the Earth crust) alternatives are coming on the scene. An interesting element to replace lithium in batteries is kalium, which is abundant on Earth (2.09 wt%), evenly distributed and characterized by a very low standard equilibrium potential (-2.93 V vs. SHE with respect to -3.09 V vs. SHE of Li+/Li) and Lewis acidity (smaller solvated ions and thus faster conduction). Nonetheless, K-ions batteries show lower volumetric and gravimetric energy density with respect to LIBs, but still they can be a good alternative for stationary storage enabling renewable energy use in the electricity grid and reducing the impact on future lithium needs. Even if this technology is receiving increasing attention from the research community, among all the post Li-ion systems K-ion batteries are welcomed with some perplexities. Indeed, even if I can count very limited research experience, the most asked question to me is the simplest: “Do they really work?”. Yes, they actually do. As a matter of facts, my contribution is meant to show some results achieved during the last 2 years of my research activity and which is now the main topic of my PhD thesis. Here I am presenting an in-depth electrochemical characterization on commercial carbon anodes for K-metal batteries which allowed us to get insights on the storage mechanism of bigger K-ions which suit better amorphous structures; K-ions were found able to insert into both amorphous and anatase TiO2 nanotubes with promising capacity retention; many polymer electrolytes were found suitable to guarantee in K-ion systems high ionic conductivity, homogeneous ions transference and stable interfaces for long cycling results. Among them a Kraft lignin matrix crosslinked with poly(ethylene glycol) diglycidyl ether provided glorious stability at the potassium-metal interface, allowing to reach 800 stable and performing cycles. Furthermore, knowing in advance their final use, we have the chance to already design PIBs for large scale commercialization to be sustainable and low cost. In light of this consideration, as well as for the above-mentioned electrolyte, a highly porous carbon material has been successfully synthetized starting from the sustainable and low cost lignin and employed as anode for potassium-metal batteries. But what can be done next to improve this technology that is in its infancy? To conclude, these results may represent the validation of all the kalium premises as the perfect lithium allay toward the energy transition and the encouragement for increasing future studies on K-ion batteries.