Recent concerns about the availability of raw materials for lithium-ion batteries (LIBs) have led to an increased interest in alternative secondary battery technologies. Recently, from about 2010 on, researchers’ attention shifted back to sodium-ion batteries (NIBs) as they offer advantages like the replacement of the copper current collector of the anode by aluminum and low cost and abundant Na-reserves instead of relatively high cost and poorly distributed Li-reserves. These advantages are considerable, since NIBs show a comparable electrochemical performance to LIBs.¹

A significant advantage of potassium-ion batteries (KIBs), if compared with NIBs, is the lower potential of K/K⁺ related to the standard hydrogen electrode (SHE). The standard potentials are reported as −2.71 V for Na/Na⁺, −2.94 V for K/K⁺ and −3.04 V for Li/Li⁺.² Therefore, in theory, KIBs should deliver cell voltages similar to LIBs and higher than NIBs. Nevertheless, it needs to be considered that the higher radius and increased mass of K-ions result in decreased gravimetric and volumetric energy densities (76 pm and 6.941 g mol^-1 for Li⁺; 100 pm and 22.990 g mol^-1 for Na⁺; 140 pm and 39.098 g mol^-1 for K⁺).^2,3 Taking these aspects into account, KIBs could potentially show a combination of the advantages of LIBs and NIBs without suffering of their drawbacks.

With this work we demonstrate as positive and negative K-ion materials, including a K-ion full cell, may show interesting electrochemical performances which are worth to be investigated in greater detail by a wider scientific community.

References

1. N. Yabuuchi, K. Kubota, M. Dahbi, and S. Komaba, Chemical Reviews, 114, 11636–11682 (2014).

2. S. Komaba, T. Hasegawa, M. Dahbi, and K. Kubota, Electrochemistry Communications, 60, 172–175 (2015).

3. M. E. Wieser et al., Pure and Applied Chemistry, 85, 2013 (2013).