Revisiting Intercalation Anode Materials for Potassium-Ion Batteries.

Potassium-ion batteries (KIBs) have attracted significant attention in recent years as a result of the urgent necessity to develop sustainable, low-cost batteries based on non-critical raw materials that are competitive with market-available lithium-ion batteries. KIBs are excellent candidates, as they offer the possibility of providing high power and energy densities due to their faster K diffusion and very close reduction potential compared with Li/Li. However, research on KIBs is still in its infancy, and hence, more investigation is required both at the materials level and at the device level. In this work, we focus on recent strategies to enhance the electrochemical properties of intercalation anode materials, i.e., carbon-, titanium-, and vanadium-based compounds. Hitherto, the most promising anode materials are those carbon-based, such as graphite, soft, or hard carbon, each with its advantages and disadvantages. Although a wide variety of strategies have been reported with excellent results, there is still a need to improve the standardization of the best carbon properties, electrode formulation, and electrolyte composition, given the impossibility of a direct comparison. Therefore, additional effort should be made to understand what are the crucial carbon parameters to develop a reference electrode and electrolyte formulation to further boost their performance and move a step forward in the commercialization of KIBs.