A unique Co3O4 material, with a peony-like architecture assembled with ultrathin porous nanosheets, could display unprecedented rate capabilities when acting as the anode for lithium-ion batteries.

Investigations into conversion-type materials such as transition-metal oxides have dominated in energy-storage systems, especially for lithium ion batteries in recent years. A common understanding of taking account of high energy density and high power density allows us to design reasonable electrodes. In this study, the unique Fe3O4@nitrogen-doped carbon (denoted as Fe3O4@NC) nanocapsule with self-formed channels was synthesized based on a facile hydrothermal-coating-annealing route. With respect to the effect of this rational architecture on lithium-storage performance, excellent behavior (a high reversible capacity of 480 mAh g–1) could be maintained at 20 A g–1 during 1000 cycles, with an average Coulombic efficiency of 99.97%. It also means that such a Fe3O4@NC electrode can meet a fast-charge challenge (end-of-charge within ∼2 min). By a series of investigations, we certainly considered that uniform carbon coating improved electrical conductivity and acted as a buffer layer to accommodate volume variations of Fe3O4 nanoparticles during cycling. It is more interesting that self-formed channels can effectively shorten the ion diffusion path and provide a necessary space to buffer volume expansion as well. Benefiting from these synergetic advantages, this Fe3O4@NC nanocapsule also delivered outstanding electrochemical performances in full cells.

Antimony is a competitive and promising anode material for sodium‐ion batteries (SIBs) due to its high theoretical capacity. However, the poor rate capability and fast capacity fading greatly restrict its practical application. To address the above issues, a facile and eco‐friendly sacrificial template method is developed to synthesize hollow Sb nanoparticles impregnated in open carbon boxes (Sb HPs@OCB). The as‐obtained Sb HPs@OCB composite exhibits excellent sodium storage properties even when operated at an elevated temperature of 50 °C, delivering a robust rate capability of 345 mAh g−1 at 16 A g−1 and rendering an outstanding reversible capacity of 187 mAh g−1 at a high rate of 10 A g−1 after 300 cycles. Such superior electrochemical performance of the Sb HPs@OCB can be attributed to the comprehensive characteristics of improved kinetics derived from hollow Sb nanoparticles impregnated into 2D carbon nanowalls, the existence of robust SbOC bond, and enhanced pseudocapacitive behavior. All those factors enable Sb HPs@OCB great potential and distinct merit for large‐scale energy storage of SIBs.

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