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

Abstract

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 the 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 Lithium-ion batteries (LIBs) are currently dominating the global portable electronics and electric vehicles market, but as the demand for LIBs rises, lithium (Li) supply might soon become the limiting factor to LIB production.1 Li and cobalt (Co) supply are under risk according to a study by British Geological Survey.2 The matter gets even worse as the need for grid-scale energy storage increases with the integration of intermittent renewable technologies such as photovoltaics and wind into the grid. Thus, a large-scale implementation of energy storage requires a battery technology that is based on cheap and abundant raw materials. Fortunately, potential alternatives do exist, because both sodium (Na) and potassium (K) have only slightly different electrochemical properties than Li and are 1000 times more abundant in the Earth's crust than Li.3-5 While the first sodium-sulfur batteries (Na-S) date back to 1968, 6 intensive research on room-temperature sodium-ion batteries has only started in recent years. 4 Hard carbons (HCs) are currently the most promising and simplest anode materials for sodium-ion batteries (NIBs). They are extensively investigated and used in some commercial Na-ion battery cells.7 Although, there are numerous papers analyzing the synthesis and electrochemical characterization of hard carbons in [8][9][10][11][12][13][14][15][16] Na-ion 17-31 battery cells, only some papers on K-ion 32,33 battery (KIB) cells have been published. There are no systematic studies on how the same carbon electrode performs in half-cells with all three Li + , Na + and K + cation containing electrolytes and how the metal cation properties affect the charge-transfer kinetics on/in the electrode.Carbon anode materials are generally divided into three classes: graphite, non-graphitized glass-like carbon (hard carbon) which cannot be graphitized even when heat-treated at very high temperature, and sof...

Dehydration of Alginic Acid Cryogel by TiCl4 vapor: Direct Access to Mesoporous TiO2@C Nanocomposites and Their Performance in Lithium‐Ion Batteries

“…In contrast, the Nyquist plot of CG‐TiO 2 @C exhibited an additional depressed semicircular arc at a medium frequency, which should be related to a semi‐infinite diffusion‐like processes as often observed in hard carbon materials . However, the appearance of this semicircle was very different from that of A600, suggesting that the carbon matrix in CG‐TiO 2 @C was not the same as that in A600.…”

Etching Asymmetric Germanium Membranes with Hydrogen Peroxide for High‐Capacity Lithium‐Ion Battery Anodes

“…The Nyquist plots of DC PAN Ge Mem 30 s shown in Figure c were also fitted using an equivalent circuit consisting of R s , R ct , R SEI , and W d . R s is electrolyte resistance, R ct is the charge transfer resistance of Ge powders, R SEI is the resistance from the SEI layer, constant phase element (CPE) is the capacitive resistance from the double layer, and W d stands for Warburg diffusion impedance (Figure d) . Figure d also shows the fitted values of R s , R ct , and R SEI resistances.…”

Carbon Anodes for Nonaqueous Alkali Metal‐Ion Batteries and Their Thermal Safety Aspects

“…[177] Heteroatomic doping has been an effective tool for enhancing electrochemical performance with PIB carbon anodes, with nitrogen-rich hard carbon microspheres obtaining a capacity of 154 mAh g −1 at an immense 72 C rate, due to the enhanced adsorption capability and electronic conductivity. [179] A few soft carbon materials have been investigated for PIB anode. [178] When nanospheric hard carbon electrodes were compared across the three alkali metal-ion batteries via EIS, the highest diffusion resistance was measured for the potassium system, due to slow mass-transfer and Faradaic charge transfer processes.…”