Strategy for practically constructing high-capacity sulfur cathode by combining sulfur-hierarchical porous graphitic carbon composite with surface modification of polydopamine

Abstract Driven by intriguingly high energy density up to 2600 Wh/kg, lithium sulfur (Li-S) battery is considered as one of the most promising energy storage devices compared with conventional lithium ion battery. The main obstructions plaguing Li-S batteries associated with the electrical resistivity of sulfur/lithium sulfides, the dissolution of polysulfides in ether-based electrolyte and the large volume variation, result in poor cycling performance and rate capability. Here, we develop a polymer optimized cathode that is polydopamine layer coated on the surface of sulfur loaded hierarchical porous graphitic carbon composites (HPGC-S-PD) by a simple in-situ polymerization method toward the highly suppressed shuttle effect, thus the significantly improved cell performance. Attributed to the superiorities of the structure engineering including the strengthened polysulfide trapping, accelerated ionic conductivity and stable electrode construction, this cathode can deliver an excellent cycling performance over 700 cycles at 1 C, a high areal capacity of 7.25 mAh/cm2 with raised sulfur loading as high as 5.15 mg/cm2. Meanwhile, the obtained cathode can work well with a lower E/S ratio compared with the non-coated cell, which suggests the immense possibility for yielding a practically Li-S battery with high energy density based on this electrode architecture. Strikingly, the pouch cell with optimized cathode material can realize an energy density of 272 Wh/kg after 40 cycles at 0.1 C. This rational design of sulfur cathode combining HPGC with polymer coating by a scalable strategy provides a comprehensive understanding of the structural engineering for sulfur cathodes in pursuit of practically high performance Li-S batteries.