ИСТИНА

Phase-transforming cathode materials have been extensively studied for both Li-ion (olivine LiFePO4) and Na-ion (Na3V2(PO4)3) batteries. In particular, LiFePO4 material has become a model system for the investigation of intercalation induced phase transformation mechanisms.1 Most of the state-of-the-art research on the phase-separating intercalation materials focuses on the elucidation of phase transformation mechanisms as well as on the theoretical assessment of the nucleation barrier heights based on the evidence from structural and microscopic single particle-level experiments.2 In this work, we show that the new phase nucleation appears to be a characteristic rate-determining step for a wide range of intercalation materials (LiFePO4, V2O5, Prussian blue analogues, etc.). We demonstrate that the nucleation rates (probabilities of critical nucleus formation) can be straightforwardly determined from the electrochemical experimental data. We propose a simple approach based on the classical nucleation theory toward interpreting electrochemical cyclic voltammetry and chronoamperometry data for phase-transforming electrodes.3 Experimental data analysis illustrates the validity of the applied approaches, which allows developing diagnostic criteria for distinguishing slow nucleation rate control from other possible rate-determining steps.