Hierarchically porous γ-Ti3O5 hollow nanospheres as an effective sulfur host for long-life lithium-sulfur batteries

Abstract

Polysulfides shuttle and volume change on cathode seriously degrade the energy density of lithium-sulfur batteries based on sulfur cathodes. Here, we successfully synthesize hierarchically porous γ-Ti3O5 hollow nanospheres (p-Ti3O5) via carbothermal reduction for the first time. The p-Ti3O5 has the feature of large surface area (444.7 m2 g−1), great pore volume (0.89 cm3 g−1), and hierarchical pores. The high electronic conductivity of γ-Ti3O5 phase and chemical interaction between titanium ions and polysulfides are beneficial for ion/electron migration and polysulfide confinement. The unique structure of the obtained p-Ti3O5 ensure sufficient active sites for chemical reaction, provide moving pathways for ion/electron migration, and inhibit structure collapse of cathode electrode during discharge/charge process. When the sulfur cathode is embedded in the p-Ti3O5composite, it provides a reversible discharge capacity of 585 mAh g−1 after prolonged 900 cycles at 0.5C rate with a capacity decay of 0.053% per cycle. It outperforms Ti3O5/S and TiO2/S cathodes on electrochemical performance. Even when sulfur loading is 5.8 mg cm−2, p-Ti3O5/S electrode exhibits a considerable capacity of 5.9 mA h cm−2. This work emphasizes advantages of high conductivity, chemical confinement of polysulfides, and hierarchically porous structure of p-Ti3O5 on sulfur cathode electrode for long-life lithium-sulfur batteries.