Toward highly reliable K‐ion half and full coin cells

To develop high energy and high power potassium-ion batteries (KIBs), performance need to be evaluated in full-cells instead of half-cells based on the highly reactive K metal that leads to misinterpretation of the results. However, assembling KIBs full-cells is not trivial as many parameters are critical to the obtained performance. This work demonstrates approaches to assemble reliable K-ion full-cells using graphite and KVPO4F0.5O0.5 based electrodes. First, the optimal separators choice/number and electrolyte choice/volume are determined in half-cells then the optimal electrolyte volume is determined in full-cells. Importantly, the electrolyte volume should be fixed to about 4 times the porosity volume for both half- and full-cells. Then, using 3-electrodes cells, the optimal negative/positive (N/P) diameter ratio then the optimal N/P capacity ratio are determined to be 1.16 ±0.2. Finally, these approaches allow assembling KVPFO//graphite coin-cells with an energy density of about 47 Wh kgdevice-1 using a high N/P loading ratio of 4/10 (in mgactive-material cm-2). Overall, this work can be used as a guide to assemble any KIBs full-cell system and thus paves the way to the determine the best negative/positive materials combination in order to develop efficient KIBs.