Confined Iterative Self-Assembly of Ultrathick Freestanding Electrodes with Vertically Aligned Channels for High Areal Capacity Sodium-Ion Batteries

Electrodes with a high areal capacity are critical for developing high-energy-density sodium-ion batteries (SIBs). The free-standing thick electrode is a promising candidate among the state-of-art electrodes, since it has the advantages of high areal mass, binder-free, current-collector-free, and no carbon additive; thus, the whole mass of the electrode is an active material that can contribute to capacity. However, enhancing areal density by introducing thick electrodes impinges on the transport of charge carriers including ions and electrons. Here we designed and synthesized an ultrathick (1500 μm) free-standing foam, which is a carbon framework with 1T-MoS2 nanosheets embedded in the vertically aligned channel wall. To tune the areal mass and morphology of the as-obtained foam, a confined iterative self-assembly strategy was proposed. The Na+ storage behavior was studied by using the as-obtained foam as a free-standing electrode against Na metal. Consequently, it displays good cycle stability even with a high areal mass of 20.74 mg cm–2 and delivers an astonishing reversible areal capacity of 19.75 mAh cm–2 at 0.01 A g–1, which greatly exceeds that of most sodium storage materials. The proposed confined iterative self-assembly strategy for fabricating thick electrodes opens new avenues for high areal capacity batteries.