Dense Graphene Monolith for High Volumetric Energy Density Li-S Batteries

Despite the outstanding gravimetric performance of lithium-sulfur (Li-S) batteries, their practical volumetric energy density is normally lower than that of lithium-ion batteries, mainly due to the low density of nanostructured sulfur as well as the porous carbon hosts. Here, a novel approach is developed to fabricate high-density graphene bulk materials with ink-bottle-like mesopores by phosphoric acid (H3PO4) activation. These pores can effectively confine the polysulfides due to their unique structure with a wide body and narrow neck, which shows only a 0.05% capacity fade per cycle for 500 cycles (75% capacity retention) for accommodating polysulfides. With a density of 1.16 g cm(-3), a hybrid cathode containing 54 wt% sulfur delivers a high volumetric capacity of 653 mA h cm(-3). As a result, a device-level volumetric energy density as high as 408 W h L-1 is achieved with a cathode thickness of 100 mu m. This is a periodic yet practical advance to improve the volumetric performance of Li-S batteries from a device perspective. This work suggests a design principle for the real use Li-S batteries although there is a long way ahead to bridge the gap between Li-S batteries and Li-ion batteries in volumetric performance.