Riveting Nucleation Enabled Long Cycling Life Calcium Metal Anodes

Calcium metal batteries with high capacity and low cost are promising alternatives to Li-ion batteries for large-scale energy storage. However, its development is crucially impeded by the irreversible Ca metal anode, which is highly associated with uncontrollable Ca plating/stripping. Here, we report a new riveting strategy to regulate the nucleation and growth of a Ca metal anode in the 3D structure of a carbon nanotube film (CNF) by introducing in situ-formed Na metal mediators. Na metal mediators are found to first deposit in the CNF substrate prior to Ca nucleation and subsequently induce dense and uniform Ca plating due to their thermodynamically favorable kinetics. Therefore, even at a high current density of 10 mA cm^-2 and a high capacity of 5 mAh cm^-2, it realizes the uniform nucleation and growth of dendrite-free Ca metal. Moreover, an unprecedented cycling life of over 800 cycles is also achieved for Ca metal batteries with a high coulombic efficiency above 98.4%. This work demonstrates the significance of a riveting strategy to enable the superior performance of Ca metal batteries by regulating the plating/stripping behaviors of Ca metal anodes and paves a new way for the development of Ca metal batteries.