An interlayer composed of a porous carbon sheet embedded with TiO2 nanoparticles for stable and high rate lithium–sulfur batteries

Abstract

The shuttling of lithium polysulfides (LiPSs) in lithium–sulfur (Li–S) batteries results in low sulfur utilization and fast capacity decay, hindering their practical applications. Constructing an interlayer is an efficient way to block the LiPS shuttling, but maintaining a low Li ion diffusion resistance with such an interlayer is hard to achieve. Herein, a thin porous carbon nanosheet embedded with TiO₂ nanoparticles (denoted PCNS-TiO₂) was used to fabricate an interlayer on the separator, which effectively solves the above problem. The PCNS-TiO₂ was prepared by using the Ti₃C₂T_x MXene as the two-dimensional (2D) template directing the porous carbon sheet formation, and the Ti₃C₂T_x transformed into TiO₂ nanoparticles embedded in the PCNS. The decomposition of the MXene eliminates the ion blocking effect by the 2D nanosheet structure. The thin and hierarchical porous structure allows fast Li ion diffusion across the interlayer, and at the same time, the porous structure and the strong adsorption ability of TiO₂ effectively block the polysulfide diffusion. Thus, the Li–S battery with this interlayer shows good rate performance with a high capacity of 627 mA h g⁻¹ at 2 C. Meanwhile, stable cycling performance is also achieved, showing a low capacity decay of 0.063% per cycle after 300 cycles at 0.5 C.