Encapsulation of Titanium Disulfide into MOF-Derived N,S-Doped Carbon Nanotablets Toward Suppressed Shuttle Effect...

Titanium disulfide (TiS₂) is a promising anode material for sodium-ion batteries due to its high theoretical capacity, but it suffers from severe volume variation and shuttle effect of the intermediate polysulfides. To overcome the drawbacks, herein the successful fabrication of TiS₂@N,S-codoped C (denoted as TiS₂@NSC) through a chemical vapor reaction between Ti-based metal-organic framework (NH₂-MIL-125) and carbon disulfide (CS₂) is demonstrated. The C─N bonds enhance the electronic/ionic conductivity of the TiS₂@NSC electrode, while the C─S bonds provide extra sodium storage capacity, and both polar bonds synergistically suppress the shuttle effect of polysulfides. Consequently, the TiS₂@NSC electrode demonstrates outstanding cycling stability and rate performance, delivering reversible capacities of 418/392 mAh g^-1 after 1000 cycles at 2/5 A g^-1. Ex situ X-ray photoelectron spectroscopy and transmission electron microscope analyses reveal that TiS₂ undergoes an intercalation-conversion ion storage mechanism with the generation of metallic Ti in a deeper sodiation state, and the pristine hexagonal TiS₂ is electrochemically transformed into cubic rock-salt TiS₂ as a reversible phase with enhanced reaction kinetics upon sodiation/desodiation cycling. The strategy to encapsulate TiS₂ in N,S-codoped porous carbon matrices efficiently realizes superior conductivity and physical/chemical confinement of the soluble polysulfides, which can be generally applied for the rational design of advanced electrodes.