Since 2015, when a Japanese team showed that potassium could be electrochemically intercalated in graphite, there has been growing interest in K-ion technology and hundreds of publications covering this advancement every year. The logic behind this is that K-ion functions without nickel, cobalt, lithium, or copper – which are all critical and/or toxic materials – and requires far less energy to produce than lithium-ion.
Future batteries on a par with LFP/Graphite
Recent advancements at Liten are part of this fundamental shift, demonstrating that beyond these virtues, K-ion cells also have promising performances. “We measured discharge capacities of 116 mAh/g at 3.6 V and a residual capacity of 80% after 120 cycles. We therefore foresee future products on a par with LFP/Graphite," says David Peralta, who is overseeing such developments at Liten.
These findings are from a thesis carried out between 2021 and 2024, which led to two patent applications and a publication. The aim was to develop a full system while working concurrently on an iron- and manganese-based cathode material, Prussian White; a specific form of graphite for the anode, different from that used in Li-ion; and an electrolyte that compensates for the high reactivity of potassium, thereby preventing a loss of capacity during cycling.
Next step: improve both the cells and materials
“Every matter has been attended to, except for the assembly and optimization of cells due to time constraints. That being said, there are no more major obstacles to overcome, but rather many improvements to be made to the cell and these materials. That's why we are feeling optimistic moving forward."
For example, the synthesis of Prussian White (via precipitation in water at room temperature) eventually led to a yield of 20 grams per batch, as opposed to just 1 gram initially. However, the shape of the particles leaves a lot to be desired, whether nanometric in size or irregularly shaped twinned crystals. “With spherical particles, which are easier to compact, we will be able to significantly increase the density of the active material in the cathode, and thus the energy density."
Three concurrent projects to intensify efforts in this area
Researchers already foresee a second generation of K-ion cells, in which the materials and cells will be optimized together, as well as a third for which alternative materials will be explored to identify new areas where progress can be made.
This will give rise to a new series of projects aimed at developing and enhancing the performance of K-ion cells. We must also point out that all these efforts mark a significant development, despite the many years of research that still lie ahead. In other words, there are high hopes for K-ion technology.
Credit CEA - D. Guillaudin