Perovskite La0.6Sr0.4CoO3-δ as a new polysulfide immobilizer for high-energy lithium-sulfur batteries

To tackle the issue of low sulfur utilization and inferior cycle stability of sulfur cathode, we first report a new perovskite-type La0.6Sr0.4CoO3-delta (LSC) immobilizer to anchor the intermediate polysulfides via chemical interaction. The experimental results and theoretical calculations demonstrate that Sr doping results in valence variation in Co along with oxygen vacancy; The Co ions with mixed valence have strong adsorption to the polysulfide ions while the existence of oxygen vacancy enhances the binding strength between Li2S4 and LSC. Based on LSC, a dual coxial LSC/S@C nanocable is successfully designed and fabricated. With a sulfur loading of 2.1 mg cm(-2), the LSC/S@C cathodes demonstrate a high reversible capacity of 996 mA h g(-1) at 0.5 degrees C and an outstanding cycle stability with only 0.039% capacity fade per cycle over 400 cycles. Even with a high sulfur loading of 5.4 mg cm(-2), the LSC/S@C cathode can still deliver similar sulfur utilization and excellent cycling stability. The excellent cycle stability benefits from the chemical interaction between LSC and polysulfides, and the physical entrapment of the carbon shell. Moreover, the highly conductive LSC@C host and the porous interconnected fiber web-like architecture facilitate the mass transfer during charge/discharge process synchronously.