Operando Deconvolution of Solvation Desolvation Energy and Interfacial Charge Transfer
Operando deconvolution isolates ion desolvation from interfacial charge transfer, enabling electrolyte formulations that eliminate low-temperature power loss.
Eyring Kinetics
Meaning
Chemical reaction rate theory describes the transition from reactants to products through an activated transition state. For lithium batteries, Eyring kinetics models the temperature-dependent rate of charge transfer and desolvation at the electrode-electrolyte interface. The model utilizes activation enthalpy and entropy to characterize the free energy barrier of the rate-limiting step.
Thermodynamic Interpretation
Traditional Arrhenius equations simplify rate variations with temperature by using a single activation energy, whereas this framework distinguishes the entropic and enthalpic contributions to the reaction barrier. The rate constant depends directly on the transition-state energy relative to the initial state. A high activation enthalpy indicates a strong temperature dependence, which worsens performance under cold conditions.
Entropic terms capture the change in molecular order as the lithium ion moves from the liquid phase to the activated complex.
Rate Analysis
Calculations based on this transition-state theory assist in determining the mechanism of charge transfer across the phase boundary. High precision measurements of current density at varying temperatures provide the experimental data needed to construct Eyring plots. Analyzing the slope and intercept of these plots yields the activation enthalpy and activation entropy.
This thermodynamic detail explains how different solvent shells influence the ease of charge transport.
Electrochemical Consequence
Sourcing engineers use these kinetic parameters to select electrolyte formulations that maintain low resistance at extreme temperatures. High-performance batteries require a low activation enthalpy for the desolvation step to prevent lithium plating during fast charging. Knowing these values allows cell designers to specify salts and solvents that lower the free energy barrier at the anode surface.
By selecting materials according to these kinetic constraints, manufacturers produce cells that achieve high power densities and stable long-term cycling.