Integrating hierarchical porous nanosheets in the design of carbon cloth-based sandwiched sulfur cathodes to achieve high areal capacity in lithium sulfur batteries†
Due to the relatively small surface area of carbon cloth and its low possibilities for further architecturing, various hierarchical structures are in situ grown on carbon cloth in the fabrication of high sulfur loading cathode to achieve outstanding electrochemical properties. Despite high specific capacities in previously reported cathodes, areal capacity is unsatisfactory due to loading of low-mass sulfur. New techniques are still demanding to fulfill simultaneous achievements of high sulfur loading and high areal capacity. Herein, a three-dimensional interconnected network composed of Co3O4 nanosheets is constructed for the first time on carbon cloth for high sulfur loading. In terms of this three-dimensional interconnected network, Co3O4 nanosheets are not only grown on carbon fiber surfaces which can significantly increase the surface area for sulfur anchorage compared to pristine carbon cloth, but also within inter-fiber spacing where two adjacent carbon fibers are bridged, which is not yet achieved in any previously reported hierarchical structures of carbon cloth-based sulfur cathodes. Thus, this functionalized carbon cloth can provide significantly enlarged spaces for distribution of high mass loading sulfur. The thus-obtained sandwich-type sulfur cathode that integrates the functionalized carbon cloth and a pristine carbon cloth interlayer delivers a high areal capacity of ∼3.63 mA h cm−2 at a sulfur mass loading of ∼5.5 mg cm−2 and a capacity retention rate of ∼93% after 200 discharge/charge cycles, which demonstrates a superior areal capacity to most of the previously reported carbon cloth-based sulfur cathodes. This study presents a new strategy for constructing a three-dimensional interconnected network to achieve high mass loading of active materials on flexible supports.