Absolute and Electrochemical Scales of Electrolyte Redox Stability

1 Absolute and Electrochemical Scales of Electrolyte Redox Stability 

In order to establish a connection between the quantities extracted from QC calculations and the measured oxidation stability, the energy cycle shown in Fig. 8.1 is commonly used. The absolute oxidation potential of a complex M relative to an electron at rest in vacuum [ °abs(M)], is given by (8.1)  

The predicted values from QC calculations of the absolute E absCM) need to be converted to the commonly used standard hydrogen electrode (SHE) or Li+/Li potential scale in order to compare them with experimental data. There are two main approaches for accomplishing this. In the first approach, well-established data for aqueous electrolytes are used to connect the absolute and electrochemical scales. This approach neglects the influence of the nature of a particular aprotic solvent on the lithium free energy of solvation. The International Union of Pure and Applied Chemistry (lUPAC)-recommended values [4] for the absolute SHE potential in 

In the second approach, an implicit solvent such as the polarized continuum method (PCM), an explicit solvent, or a combination of these methods is used in order to calculate the lithium free energy of solvation so that the conversion factor is specific for the electrolyte of interest needed for the cycle shown in Fig. 8.1b. A number of groups [7, 8] have used DFT calculations to relate the absolute and LiV Li potential scales using the thermodynamic cycles shown in Fig. 8.1a, b for the 

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