Design of grid-like triple-carbon matrix confined ultrafine CoTe2 nanocrystals toward durable and fast potassium storage

Abstract

Developing sophisticated electrode materials has been considered a promising strategy for enhancing the performance of potassium storage. CoTe₂, a potential anode material, has been extensively investigated due to its high theoretical specific capacity. However, the challenge remains in constructing CoTe₂ structures with a low aggregation, adequate volume buffer space, fast reaction kinetics, and minimal dissolution for intermediate phases. In this work, we propose a porous grid-like N-doped triple-carbon confined CoTe₂ (CoTe₂@T-NC) anode material to overcome these challenges. The porous grid-like carbon matrix not only disperses CoTe₂ particles and inhibits their aggregation during cycling processes, but also mitigates volume expansion by reducing the particle size of CoTe₂. Furthermore, the highly interconnected carbon networks provide numerous channels for efficient conduction of both electrons and potassium ions, which significantly enhances reaction kinetics. Additionally, the nitrogen-rich carbon matrix effectively anchors the intermediate phases (K₂Te₃ and K₅Te₃) and prevents their dissolution into the electrolyte. The optimized CoTe₂@T-NC electrode exhibits high specific capacity (428.8 mA h g⁻¹ at 0.05 A g⁻¹), reliable cycling stability (1500 cycles at 2.0 A g⁻¹), and excellent rate performance (215.9 mA h g⁻¹ at 3.0 A g⁻¹). Through various in situ and ex situ techniques, along with theoretical calculations, we have gained a clear understanding of the “intercalation–conversion” reaction mechanism of CoTe₂ and the strong chemical adsorption of pyrrole-N and pyridine-N sites on K₂Te₃ and K₅Te₃. This work deepens our understanding of the structure–performance relationships in the CoTe₂-based electrode, which is beneficial for the development of potassium storage electrode materials with outstanding overall performance.