Thermodynamics of Lithium Intercalation in Randomly Oriented High Graphene Carbon

Abstract

This paper covers details of systematic investigation of the thermodynamics (entropy and enthalpy) of intercalation associated with lithium ion in a structurally novel carbon, called Randomly Oriented High Graphene (ROHG) carbon and graphite. Equilibrated OCV (Open Circuit Voltage) versus temperature relationship is investigated to determine the thermodynamic changes with the lithium intercalation. ROHG carbon shows entropy of 9.36 J·mol−1·K−1 and shows no dependency on the inserted lithium concentration. Graphite shows initial entropy of 84.27 J·mol−1·K−1 and shows a strong dependence on lithium concentration. ROHG carbon (from −90.85 kJ mol−1 to −2.88 kJ mol−1) shows gradual change in the slope of enthalpy versus lithium ion concentration plot compared to graphite (−48.98 kJ mol−1 to 1.84 kJ mol−1). The study clearly shows that a lower amount of energy is required for the lithium ion intercalation into the ROHG structure compared to graphite structure. Randomly oriented graphene platelet cluster structure of ROHG carbon makes it easier for the intercalation or deintercalation of lithium ion. The ease of intercalation and the small cluster structure of ROHG as opposed to the long linear platelet structure of graphite lead to higher rates of the charge-discharge process for ROHG, when used as an electrode material in electrochemical applications.