Optimizing Heat-Treated Al-BDC@TiO2 to Improve the Electrochemical Properties of Lithium-Sulfur Batteries.

Lithium-sulfur batteries (Li-S) are highly promising due to their high energy density and specific capacity; however, the poor conductivity of the active material leads to slow reaction kinetics, and the shuttle effect of the intermediate product lithium polysulfides leads to rapid capacity decay. Here, the effective encapsulation of Al-BDC by TiO₂ particles is achieved by encapsulating an aluminum-based metal organic framework (Al-BDC) with terephthalic acid as the organic ligand and heat-treating at different temperatures. This method shows that the TiO₂ particles can effectively encapsulate Al-BDC while maintaining the structural stability of Al-BDC after heat treatment at 400°C. The TiO₂ crystallization is disordered after heat treatment at 300°C, and the TiO₂ is exfoliated and the Al-BDC is collapsed after heat treatment at 500°C. In addition, TiO₂ particles can be partially filled into the pores of Al-BDC. Therefore, Al-BDC@TiO₂-400 can effectively inhibit the shuttle of polysulfides, and the corresponding Li-S batteries can achieve relatively high discharge specific capacity, rate performance and cycling stability. In particular, the Al-BDC@TiO₂-400@S can achieve an initial discharge specific capacity of 907.6 mAh g⁻¹ at 0.1C, and 686.5 mAh g⁻¹ at 2C with remained capacity of 379.8 mAh g⁻¹ after 400 cycles. [ABSTRACT FROM AUTHOR]