Development of Bicontinuous Carbon Foam/ Metal Sulfide Composites As Free-Standing Electrodes for Lithium Ion Storage

Abstract

We designed and fabricated a series of bicontinuous carbon foam/metal sulfide composite with hierarchical porosities as a high performance free-standing anode electrode for lithium ion batteries. The synthetic method involves the scalable nanocasting process of layered structured MxS (M=Fe, Sn, Cu) using the high internal phase emulsion polymer (polyHIPE) as the structural support as well as the electronic conducting network. The as-developed C/MxS SnO2 electrode is highlighted by several innovative design concepts: firstly, macroporous carbon foam derived from the pyrolysis of polyHIPE could serve as the structural support as well as the sulfur source for the MxS synthesis; secondly, the C/ MxS bicontinuous network not only provides facile electronic transport and electrolyte percolation, but remove the necessity of usage of binder, carbon additive and massy metal current collector; thirdly, the off-stoichiometric zero valent metal particles is designed to provide the dual functionalities of electrically wiring the electroactive materials as well as the catalytic effect for graphitization of carbon. The electrochemical measurements of these C/ MxS electrodes were therefore conducted to demonstrate the high specific capacity (500 ~ 700 mA h g-1) and excellent rate capability up to 4 A g-1, which presents the best cycling performance among metal sulfide-based free-standing electrodes to date (C/FeS) and thus the superior structural design of electrodes. Finally, the storage mechanism of metal sulfides was investigated through the in-situ characterization techniques and Mössbauer spectroscopy.