Room-Temperature Calcium Intercalation into Graphite Catalyzed by Sodium

Abstract

Calcium (Ca) insertion into graphite (C) has been considered to require elevated temperatures, and its occurrence at room temperature (RT) has been regarded as highly unlikely. Here, we demonstrate that sodium (Na) catalysis enables the formation of superconducting CaC${}_6$ even at RT. In mixtures of Ca, Na, and graphite, the gradual development of superconducting diamagnetism and the emergence of X-ray diffraction peaks confirm the formation of CaC${}_6$ during storage at RT. The superconducting transition temperature increases with storage time, and the amount of CaC${}_6$ scales proportionally to the square root of storage time. These findings provide new insights into the mechanism of superconductivity and Na-catalyzed formation of CaC${}_6$, and highlight the potential of this RT intercalation process for practical applications such as electrode materials in Ca-ion batteries.

7 pages, 3 figures

References in corpus (6)

• Superconductivity in the Intercalated Graphite Compounds C6Yb and C6Ca
• Superconductivity of bulk CaC6
• Effective Demagnetization Factors of Diamagnetic Samples of Various Shapes
• Dramatically Accelerated Formation of Graphite Intercalation Compounds Catalyzed by Sodium
• Na-catalyzed rapid synthesis and characterization of intercalated graphite CaC6
• Accelerated Lanthanide Intercalation into Graphite Catalyzed by Na