Enhancement of long stability of Li–S battery by thin wall hollow spherical structured polypyrrole based sulfur cathode

Abstract

To enhance the long stability of sulfur cathode for a high-energy lithium–sulfur cell, a thin wall hollow spherical structured polypyrrole (T-HSSP) composed of a mono layer of PPy nano-particles is employed as a host to encapsulate the sulfur component. T-HSSP can buffer the volume expansion of sulfur during the discharge and charge processes; therefore can maintain the integrity of the sulfur electrode after long cycling. The distribution of sulfur component is maintained even after 100 charge/discharge cycles in T-HSSP, indicating the efficiency of the design in inhibiting the shuttle effect of the sulfur electrode. The composite with a sulfur content of 58.4 wt% exhibits a reversible capacity of 1563.3 mA h g⁻¹ and a discharge capacity retention over 89% during 40–200 cycles, corresponding to a sulfur utilization rate of 89.2% at 0.2 C. The excellent rate capability of the composite is demonstrated by its cycling performances at 1 C, 2 C, and 5 C for 300 cycles. Moreover, a further heating treatment is carried out to inhibit the severe capacity fade in the initial tens of cycles, and an enhanced cycling stability of the Li–S battery is achieved.