Discovering Fe3GeTe2 as an innovative ternary germanium telluride for robust and high-rate sodium/potassium-ion battery anode

Abstract

The distinguishing feature of Fe₃GeTe₂ lies in its robust in-plane chemical bonds within layers, which are interconnected by the weak van der Waals forces between adjacent layers, offering a stable framework characterized by enhanced interlayer spacing, thereby facilitating the migration of large-sized alkali metal ions. However, to date, there have been no reported studies on the ion storage performance of Fe₃GeTe₂. In this study, Fe₃GeTe₂ is synthesized via the chemical vapor transport method to assess its sodium/potassium storage capabilities. Fe₃GeTe₂ is characterized by its impressive conductivity, a distinctive layered architecture, and a notably wide interlayer spacing, all of these attributes collectively contributing to its superior ion storage proficiency in both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). Specifically, it demonstrates exceptional electrochemical performance, maintaining a capacity of 291.8 mA h g⁻¹ at 5 A g⁻¹ in SIBs and 125.0 mA h g⁻¹ over 6000 cycles at 3 A g⁻¹ in PIBs. A series of in/ex situ characterizations uncover the reaction mechanism of Fe₃GeTe₂ in the both systems, involving a combined process of intercalation, conversion, and alloying. Theoretical calculations provide further insights into the high ion adsorption affinity and diffusion kinetics of Fe₃GeTe₂ in these systems. Analytical findings reveal its superior electrochemical performance in SIBs compared to PIBs, owing to higher diffusion kinetics and reactivity. This research establishes both experimental evidence and theoretical underpinnings for the utilization of Fe₃GeTe₂ in SIBs and PIBs, opening up a new avenue for the utilization of germanium-based ternary materials in the field of energy storage.