Alkali-Metal Insertion Processes on Nanospheric Hard Carbon Electrodes: An Electrochemical Impedance Spectroscopy Study

R. Väli, A. Jänes, E. Lust
2017 Journal of the Electrochemical Society  
In this study, we report the results of electrochemical impedance spectroscopy data modelling of various battery half-cells with different alkali metal (Li, Na, K) salts. Test results of electrochemical half-cells were evaluated for the D-glucose derived hard carbon negative electrode in 1.0 M LiPF 6 + EC:DMC (1:1 volume ratio), 1.0 M NaPF 6 + EC:DMC (1:1), 1.0 M NaClO 4 + PC, 0.8 M KPF 6 + EC:DEC (1:1) and 0.8 M KPF 6 + EC:DMC (1:1) solutions at 0.5 mV s −1 potential scan rate measured within
more » ... he potential region from 0.05 V to 1.2 V (vs Me/Me + ) (where Me is Li, Na or K). Modelling of electrochemical impedance spectroscopy data was employed to characterize alkali metal insertion processes in/on D-glucose derived hard carbon anode. Detailed analysis of impedance data shows that Newman equivalent circuit modified with a constant phase element can be applied for calculation of impedance spectra and fitting of calculated data to experimental ones, using non-linear least square root fitting method. Equivalent circuit fit parameters depend strongly on electrolyte composition. Very slow processes have been observed for KPF 6 + EC:DEC based half-cell. Comparatively quick metal-cation reduction and accumulation processes have been observed in NaClO 4 + PC and LiPF 6 +EC:DMC based half-cell anodes.
doi:10.1149/2.0431711jes fatcat:by7jsl5o5nhszghzvipn54vwfe