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

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.