Electrolyte-free potassium ions intercalated in 2D layered metal oxide for imitating spatiotemporal biological neural dynamics

Abstract

Alkali ions are crucial to physiological neural activities and their dynamics can be implemented in various iontronics. For the host materials for alkali ions, 2D layered materials have become the preferred choice thanks to their facilitating ion accommodation and movement between layers. Nevertheless, challenges such as the need for external electrolytes, pre-fabrication for ion intercalation, and thermodynamic stability during ion movements still persist. Consequently, the comprehensive understanding of the electrical dynamics associated with alkali ion movement has rarely been demonstrated in 2D layered materials so far. Here, we engineered an electrolyte-free high-crystalline 2D layered MnO₂ nanoplate with potassium ions by metal–organic chemical vapor deposition. The combination of potassium ions and layered MnO₂ exhibits electrically induced ion migration coupled with a subsequent phase transition, resulting in negative differential resistance. Furthermore, the material's distinct hybrid plasticity, driven by its ion dynamics, provides a sophisticated platform for sequential motion recognition, valuable for assessing continuous motion across varied subjects. Finally, we demonstrate the broad applicability of our 2D K-MnO₂ and highlight its versatility in spatiotemporal ion modulation within three-terminal structures, showing potential for future advancements.