Phase Transition Triggers Explosion-like Puffing Process to Make Popcorn-Inspired All-Conductive Anodes for Superb Aqueous Rechargeable Batteries.

The major accomplishment of electrochemical energy-storage devices is closely linked to the advent of state-of-the-art techniques to make optimal electrode systems. Herein, we demonstrate a unique popcorn-inspired strategy to develop all-conductive and highly puffed Fe⊂carbon nanopopcorns as superb anodes for rechargeable Ni/Fe batteries. Temperature-dependent systematic studies show that the nanopopcorn evolution mechanism is governed by typical phase variation from Fe2O3 nanospheres to dispersed Fe0 nanodebris, whose formation induces catalytic reconstruction/conversion from hydrocarbons to graphitic nanolayers while triggering the explosion-like instant puffing process beyond 700 °C. The as-built Fe⊂carbon hybrids with favorable loosened structures, open-up/enlarged surface areas, and intrinsically conducting nature enable great electrochemical reactivity and cyclic stability (reversible capacity higher than ∼420 mA h g-1 in all cycles without obvious capacity decay), as well as outstanding rate behaviors (∼300 mA h g-1 is still retained at ∼20 A g-1). Full-cell devices of NiO@carbon (+)//Fe⊂carbon (-) can exhibit Max. energy/power densities of up to ∼140.8 W h kg-1 and ∼15.6 kW kg-1, respectively. This work sheds a fundamental light on arts to configure puffed electrodes for advanced electrodes in various important applications while holding great promise for high-rate/capacity aqueous rechargeable batteries.