| Summary: | Huge volume expansion of electrode materials (e.g. 80% for sulfur and 310% for silicon) in the electrochemical lithiation reaction is seen as a root-cause of fast capacity fading of rechargeable lithium batteries. In this work, an effective solution is demonstrated by fabricating thin film sulfur and silicon electrodes with hierarchical structure of sulfur (or silicon) particles sandwiched between adjacent reduced graphene oxide (rGO) layers. The hierarchical films are constructed via vacuum filtration assisted layer-by-layer assembly of rGO and the respective precursor particles, i.e. zinc sulfide or silica shelled by super-sticky polydopamine. Polydopamine serves as a glue of rGO layers to furnish good mechanical integrity to the structure, and the precursor of nitrogen-doped carbon upon high-temperature calcination to ensure the electrical contacts between rGO layers. Zinc sulfide is oxidized to the electrochemically active sulfur by soaking in ferric aqueous solution, while silica is reduced to nanosized silicon in magnesium vapor at high temperature. The electrochemical studies reveal that the binder-free hierarchical electrodes can tolerate the volume change upon lithiation/delithiation, giving high initial Coulombic efficiency and good capacity retention. The rGO layers in the sulfur electrode is also found to effectively mitigate the diffusion of polysulfides into electrolyte. Keywords: Layer-by-layer, Hierarchical structure, Sulfur cathode, Silicon anode, Volume expansion
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