Renewable Polysulfide Regulation by Versatile Films toward High-Loading Lithium-Sulfur Batteries

The development of a high specific energy lithium-sulfur battery is heavily hindered by the so-called "shuttle effect". Nevertheless, as an effective strategy, most modified separators cannot block and reuse polysulfides simultaneously. Here, a unique and versatile film fabricated by nitrogen and phosphorus co-doped carbon nanofibers uniformly anchored with TiC nanoparticles is incorporated between the separator and cathode of the lithium-sulfur battery. The battery armed with this functional film exhibits a high capacity of 737.1 mA h g^-1 at 5 C with a slow capacity-fading rate of 0.06%/cycle over 500 cycles. Even when augmenting the sulfur loading to 17.1 mg cm^-2, it can achieve a capacity of 837.3 mA h g^-1 with a retention of ∼80% after 50 cycles. The TiC nanoparticles as well as heteroatom doping in the porous carbon nanofiber exhibit strong physiochemical adsorption and catalytic effect, which is proven by experiments and theoretical calculations. Thus, the diffusion of polysulfides can be effectively inhibited. Meanwhile, heteroatom doping can further enhance the conductivity and reaction activity of this film. Hence, the adsorbed polysulfides could be revived and renewed during the subsequent cycling process, which is accurately observed and confirmed by experiments for the first time.