Inactive materials matter: How binder amounts affect the cycle life of graphite electrodes in potassium-ion batteries

Recent results on the intercalation of potassium into graphite suggest that graphite might become yet again a negative electrode material of choice for an alkali-ion battery system. Compared to its mature application state in Li-ion batteries, graphite for K-ion applications is still in an early development stage. Although cycling of graphite-potassium half-cells over 200 cycles has been demonstrated, the electrodes clearly suffer from more severe capacity fading, as compared to the corresponding Li system. This study demonstrates that the capacity fade is strongly linked to the binder content in the composite electrode. High binder contents of 8 wt% (this study) or more (literature) show significant cycle life improvements over electrodes comprising of more practical binder contents of 4 wt% or less. The results highlight the need for revised or entirely new strategies to control the formation and stability of the electrode–electrolyte interphase in K-ion batteries.