On the contribution of phonons to electrochemical potential of Li-ion metal-organic frameworks

Abstract

According to Nernst equation, the prediction of equilibrium voltage in electrochemical cells involve the calculation of all contributions of the free energy, corresponding to electronic, vibrational and translational degrees of freedom. Most simulations are restricted to the electronic energy computed in the frame of DFT, mainly because accurate ab-initio investigations of electronic structure usually provides a useful approximation, while the calculations of properties for periodic structures typically involve massive computational resources. In this paper we propose a methodology that allows for the calculation of vibrational contributions to Nernst equation and show that in the case of organic materials (i.e. Li2-Mn-DOBDC electrodes) they represent an important contribution to the total electrode potential that cannot be neglected for the correct understanding of the redox mechanism.