Toward Highly Reliable Potassium‐Ion Half and Full Coin Cells

Assembling potassium-ion full-cells is mandatory to evaluate energy/power densities but it remains challenging. This study investigates parameters governing half- and full-cells performance using KVPO₄F_0.5O_0.5 and graphite electrodes. Optimal parameters are determined including electrolyte volume, N/P diameter and capacity ratios. Overall, highly reliable full-cells of 47 Wh kg_device ⁻¹ were obtained.

Abstract

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 KVPO₄F_0.5O_0.5 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 kg_device ⁻¹ using a high N/P loading ratio of 4/10 (in mg_{active-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.

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