Dramatically Accelerated Formation of Graphite Intercalation Compounds Catalyzed by Sodium

Graphite intercalation compounds (GICs) have a variety of functions due to their rich material variations, and thus, innovative methods for their synthesis are desired for practical applications. It is discovered that Na has a catalytic property that dramatically accelerates the formation of GICs. It is demonstrated that LiC_{6 n} (n = 1, 2), KC₈ , KC_{12 n} (n = 2, 3, 4), and NaC_x are synthesized simply by mixing alkali metals and graphite powder with Na at room temperature (≈25 °C), and A_E C₆ (A_E  = Ca, Sr, Ba) are synthesized by heating Na-added reagents at 250 °C only for a few hours. The NaC_x , formed by the mixing of C and Na, is understood to act as a reaction intermediate for a catalyst, thereby accelerating the formation of GICs by lowering the activation energy of intercalation. The Na-catalyzed method, which enables the rapid and mass synthesis of homogeneous GIC samples in a significantly simpler manner than conventional methods, is anticipated to stimulate research and development for GIC applications.