Growth direction control of lithium dendrites in a heterogeneous lithiophilic host for ultra-safe lithium metal batteries

Dendritic growth of the metallic lithium anode cannot be fully avoided for prolonged cycling due to the inherent thermodynamic and kinetic tendency, which causes serious safety issues. Here, we strategically control the lithium metal growth direction by designing a three-dimensional porous host with lithiophilic-lithiophobic characterized ligaments. Therefore, lithium metal can only nucleate on the lithiophilic back surface and grow toward the direction away from the separator. Such 'backside-growth' can ensure safe battery operation even when lithium dendrites exist. For a proof-of-concept study, highly lithiophilic gold layer is sputtered on backside surface of each copper foam ligament. During lithium plating, lithium nucleates on the lithiophilic backside and keeps growing conformably from the existing nuclei towards the opposite direction to the separator, and eventually forms a lithium-metal layer with highly compacted self-aligned columnar structure. The novel approach controls lithium deposition in two aspects simultaneously: growth direction and morphology. Notably, the featured surface dendrite-free anode exhibits ultra-long-term stable cycling with a high Coulombic efficiency (e.g., 95.0% after 300 cycles, 0.5 mA cm(-2), 1 mA h cm(-2)). This work may not only pave ways for building ultimate safe lithium batteries but also conceptually provides new opportunities for other metal anodes.