A lithium-sulfur full cell with ultralong cycle life: Influence of cathode structure and polysulfide additive
Lithium-sulfur batteries are highly attractive energy storage systems, but suffer from structural anode and cathode degradation, capacity fade and fast cell failure (dry out). To address these issues, a carbide-derived carbon (DUT-107) featuring a high surface area (2088 m2 g−1), high total pore volume (3.17 cm3 g−1) and hierarchical micro-, meso- and macropore structure is applied as a rigid scaffold for sulfur infiltration. The DUT-107/S cathodes combine excellent mechanical stability and high initial capacities (1098-1208 mA h gS−1) with high sulfur content (69.7 wt% per total electrode) and loading (2.3-2.9 mgS cm−2). Derived from the effect of the electrolyte-to-sulfur ratio on capacity retention and cyclability, conducting salt is substituted by polysulfide additive for reduced polysulfide leakage and capacity stabilization. Moreover, in a full cell model system using a prelithiated hard carbon anode, the performance of DUT-107/S cathodes is demonstrated over 4100 cycles (final capacity of 422 mA h gS−1) with a very low capacity decay of 0.0118% per cycle. Application of PS additive further boosts the performance (final capacity of 554 mA h gS−1), although a slightly higher decay of 0.0125% per cycle is observed.