Sulfur Compensation: A Promising Strategy against Capacity Decay in Li-S Batteries

Drastic capacity decay as a result of active sulfur loss caused by the severe shuttle effect of dissolved polysulfides is the main obstacle in the commercial application of Li-S batteries. Various methods have been developed to suppress the active sulfur loss, but the results are far from ideal. Herein, we propose a facile sulfur compensation strategy to improve the cyclic stability of Li-S batteries. The strategy is to compensate sulfur to the cathode by chemical reactions between additional sulfur and lithium polysulfides diffusing away from the cathode. The compensatory sulfur can effectively mitigate the loss of active sulfur in the cathode side caused by the shuttle effect and thus maintain the high capacity of the battery during charging and discharging for long life cycle assessments. Using this strategy, the specific capacity of the assembled Li-S batteries was maintained at >700 mA h g^-1 for more than 500 cycles at 1 C and >1000 mA h g^-1 for ∼100 cycles at 0.1 C, while the capacity of control batteries rapidly decreased to <200 mA h g^-1 under the same conditions.