(1 of 10)Uncontrollable dendritic behavior and infinite volume expansion in alkali metal anode results in the severe safety hazards and short lifespan for high-energy batteries. Constructing a stable host with superior Na/Li-philic properties is a prerequisite for commercialization. Here, it is demonstrated that the small Gibbs free energy change in the reaction between metal oxide (Co 3 O 4 , SnO 2 , and CuO) and alkali metal is key for metal infusion. The as-prepared hierarchical Co 3 O 4 nanofiber-carbon sheet (CS) skeleton shows improved wettability toward molten Li/Na. The 3D carbon sheet serves as a primary framework, offering adequate lithium nucleation sites and sufficient electrolyte/electrode contact for fast charge transfer. The secondary framework of Co/Li 2 O nanofibers provides physical confinement of deposited Li and further redistributes the Li + flux on each carbon fiber, which is verified by COMSOL Multiphysics simulations. Due to the uniform deposition behavior and near-zero volume change, modified symmetrical Li/Li cells can operate under an ultrahigh current density of 20 mA cm −2 for more than 120 cycles. When paired with LiFePO 4 cathodes, the Li/Co-CS cell shows low polarization and 88.4% capacity retention after 200 cycles under 2 C. Convincing improvement can also be observed in Na/Co-CS symmetrical cells applying NaClO 4 -based electrolyte. These results illustrate a significant improvement in developing safe and stable alkali metal batteries.
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