The Straightforward Route Towards the Theoretical Specific Free Enthalpy of Electrochemical Reactions

This paper outlines a simple yet precise method for identifying the theoretical specific free enthalpy of electrochemical reactions on basis of the ideal gas law, equilibrium thermodynamics and Faraday's law, exploiting the normative role of the standard hydrogen electrode in electrochemistry. The result of this approach are discussed in relation to four battery cell reaction examples: LiCoO₂/C₆, LiFePO₄/C₆, sodium-sulfur (NAS) and NaCl–Ni (ZEBRA). The agreement between calculated and practical values is near-excellent for even stoichiometries which bespeaks the virtually ideal nature of reversible reactions and the quality of the practical optimization efforts alike. These findings highlight the principal nature of intrinsic thermodynamic limitation to equilibrium mass transfer and its key role towards understanding reversible chemical energy storage in a global sense.