A compact 3D interconnected sulfur cathode for high-energy, high-power and long-life lithium-sulfur batteries

Sulfur cathodes in lithium-sulfur batteries (LSBs) have received a boost in electrochemical performance through developing various sulfur hosts. However, it remains great challenges in achieving fast electron and ion conduction while accommodating the dramatic volume change and suppressing severe intermediate polysulfide dissolution under practically necessary ‘3H’ conditions (high areal sulfur loading, high electrode compactness and high sulfur content). Here a compact 3D interconnected sulfur cathode is reported to satisfy the above requirements. It is constructed by self-assembly of Zn,Co-bimetallic ZIF nanoparticles, following pyrolysis and subsequent melt-diffusion of high-content sulfur. Sulfur filled into an open porous 3D carbon network (3DCN) with abundant N, Co doping and graphitic carbon species and produced a thin sulfur-coating layer on the macroporous surface of 3DCN. Such smart architecture provides multidimensional electron and ion transport pathways and shortened mass and ion diffusion length. The close contact of sulfur species with carbon-based polar host provides facilitated physiochemical adsorption and conversion reaction of polysulfides. At high areal sulfur loading of 10.9 mg cm^-2, high sulfur content of 74 wt% in the whole cathode and low electrolyte/sulfur ratio of 6 µL/mg, it delivers high gravimetric/volumetric/areal capacities of 945 mA h g^-1/867 mA h cm^-3/10.3 mA h cm^-2 at 0.1 C (1.83 mA cm^-2). At a high rate of 0.5 C (9.13 mA cm^-2), it still presents a high capacity of 8.73 mA h cm^-2 and maintains 6.35 mA h cm^-2 after 200 cycles. Therefore this work provides an instructive paradigm of rational architecture design to fabricate sulfur cathodes for practically viable Li-S batteries.