Molten-salt-derived TiS2 and TiSe2 with preserved layered structure and enhanced sodium-ion storage via post-synthesis pulverization

초록

Layered transition metal dichalcogenides (TiX2, X = S, Se) are promising electrode materials for sodium-ion batteries owing to their favorable intercalation properties and tunable electronic structures. However, achieving both high crystallinity and electrochemical accessibility remains a critical challenge, as highly crystalline materials often suffer from limited ion diffusion and low utilization of active sites. Herein, we report a sequential processing strategy consisting of molten-salt-assisted crystal growth followed by post-synthesis pulverization. TiS2 and TiSe2 were synthesized via a molten salt method, yielding highly crystalline layered structures with distinct defect-related electronic characteristics. Subsequent pulverization effectively reduced particle size while preserving the intrinsic layered framework, thereby enhancing structural accessibility. As a result, the MSM-derived TiSe2 exhibits improved sodium-ion storage performance, delivering a high initial discharge capacity of 235 mAh g-1 and demonstrating gradual electrochemical activation with enhanced capacity retention upon cycling. In contrast, Li-based systems show rapid capacity fading, highlighting the different storage behavior depending on ion species. The observed capacity evolution is characterized by gradual electrochemical activation and may involve improved electrochemical accessibility resulting from post-synthesis pulverization together with cycling-induced interfacial evolution. This work demonstrates that decoupling crystal growth and electrochemical accessibility provides an effective pathway to bridge structural integrity and functional performance in layered materials, providing a practical strategy for improving electrochemical performance in layered materials.

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