Chlorine-Gas-Free Synthesis of Predominantly Single-Phase Metal Chloride Intercalation Compounds in Graphitic Carbon by Selective Deintercalation of Ternary Systems

Metal chlorides can be intercalated into layered carbon materials via a vapor-phase method to form metal chloride graphite intercalation compounds (GICs). However, conventional approaches require prolonged reaction times under a chlorine gas atmosphere. Since CuCl2 releases chlorine gas upon thermal decomposition, the coexistence of CuCl2 eliminates the need for an external chlorine gas supply, although it inevitably leads to the co-intercalation of CuCl2. In this study, graphene-like graphite synthesized at 700 °C (GLG700) was employed as the host material, and selective deintercalation of CuCl2 was explored to synthesize NiCl2– and MnCl2–GLG700 binary intercalation compounds without chlorine gas and within a short reaction time. Based on this strategy, CuCl2–NiCl2–and CuCl2–MnCl2–GLG700 ternary intercalation compounds were first synthesized in the presence of CuCl2. Subsequent heat treatment under vacuum resulted in the selective deintercalation of CuCl2 from the ternary intercalation compounds, yielding NiCl2– and MnCl2–GLG700 in a nearly single-phase state. The present method provides a practical synthetic route for obtaining nearly single-phase metal chloride GICs without chlorine gas and with significantly reduced reaction time.