INTERPRETATION OF POTENTIAL INTERMITTENCE TITRATION TECHNIQUE EXPERIMENTS FOR VARIOUS Li-INTERCALATION ELECTRODES

Abstract

In this paper we compare two different approaches for the calculation of the enhancement factor W i , based on its definition as the ratio of the chemical and the component diffusion coefficients for species in mixed-conduction electrodes, originated from the "dilute solution" or "lattice gas" models for the ion system. The former approach is only applicable for small changes of the ion concentration while the latter allows one to consider a broad range of intercalation levels. The component diffusion coefficient of lithium ions has been determined for a series of lithium intercalation anodes and cathodes. A new "enhancement factor" for the ion transport has been defined and its relations to the intercalation capacitance and the intercalation isotherm have been established. A correlation between the dependences of the differential capacitance and the partial ion conductivity on the potential has been observed. It is considered as a prove that the intercalation process is controlled by the availability of sites for Li-ion insertion rather than by the concurrent insertion of the counter-balancing electronic species.

Lithium diffusion in Li3V2(PO4)3-based electrodes: a joint analysis of electrochemical impedance, cyclic voltammetry, pulse chronoamperometry, and chronopotentiometry data

“…This approach is described in detail in a number of publications of the authors Levi et al [27,37,61,64,[80][81][82]. It is based on the microscopic Lattice gas model.…”

“…At the analysis of calculation results according to the model equations, authors Levi et al in their works [27,37,61,64,[80][81][82] showed that the structure of materials with strong interparticle interactions (pronounced Bdouble phase behavior^with the long flat plateau on E,c dependence) produce an uncertainty of the C dif (x) function, which values are used for D calculation. Therefore, it is reasonable to carry out D determination in the materials having a extended domain of solid solution existence (sloped E,c dependence).…”

“…3a, E,c dependence of Li 3 V 2 (PO 4 ) 3 electrode is presented as obtained in three different modes: by said modified measurement procedure (curve 1), in which every measurement of the electrode potential was preceded by cell exposure in the Bopen circuit^conditions for 24 h; by the standard PITT procedure with stepwise change of potential and exposure to zero current in each stage (curves 2 and 3); and galvanostatic charge-discharge curves (4.5). Delithiation processes of Li 3 V 2 (PO 4 ) 3 electrode to form the final phase V 2 (PO 4 ) 3 and reverse lithiation have been investigated by several authors [80][81][82][83][84]. They go through the following sequence of transformations:…”

“…The thermodynamic E,c dependence of Li 3 V 2 (PO 4 ) 3 electrode has been analyzed in terms of microscopic Lattice gas model, studied in the series of works [27,37,61,64,[80][81][82]. The parameters of interparticle interactions in the material's structure, which correspond to the mid-level attractive interaction and to a wide range of solid solution were determined.…”

Spatially limited diffusion coupled with ohmic potential drop and/or slow interfacial exchange: a new method to determine the diffusion time constant and external resistance from potential step (PITT) experiments

“…The usefulness of the new method for determination of the chemical diffusion coefficients in practical intercalation electrodes for rechargeable lithium batteries will be addressed in a separate paper [22]. Detailed reviews on the specific problems encountered in obtaining and interpreting PITT data related to various practical intercalation electrodes, but with no account of ohmic and kinetic effects, have been previously published [23,24].…”