Patterned macroporous Fe3C/C membrane-induced high ionic conductivity for integrated Li–sulfur battery cathodes
To realize an Al-free cathode and to push forward the Li–S battery technology for practical applications, a multifunctional three-layer-structured Fe3C/C membrane was prepared at a large-scale via a facile phase-inversion method. The scalable yet flexible self-supporting Fe3C/C membrane is an ideal Al foil-free cathode material for high-energy and long cycling Li–S batteries. The conductive dense layer of the Fe3C/C membrane can replace the Al foil as a current collector and the finger-like macropores can host most of the sulfur active material (1.5–3.0 mg cm−2), thus buffering the volume expansion of the sulfur species and facilitating the ion/electrolyte transport for fast reaction kinetics; meanwhile, the sponge-like pores in the top layer of the composite membrane enable further S slurry loading. Density functional theory simulation (DFT) and Li2S6 adsorption measurements reveal that the doped Fe3C species in the composite membrane could effectively immobilize the S species and suppress the shuttle effect of the soluble polysulfides (LiPSs). The rationally designed Fe3C/C membrane cathodes could deliver a capacity of ∼601 mA h g−1 at 1C after 200 cycles even at a high sulfur loading of 3.4 mg cm−2, with a high areal capacity of 2.1 mA h cm−2. The cell with the sulfur loading of 3.4 mg cm−2 delivered a gravimetric energy density and volumetric energy density of 850 W h kg−1 and 1223 W h L−1, respectively. The self-supporting membrane cathode with simultaneous commercial S filling and S/C slurry coating provides an alternative sulfur loading approach for battery assembly, thus presenting a useful strategy for practical applications in high energy-density and long cycling Li–S batteries.