Correlation of capacity fading processes and electrochemical impedance spectra in lithium/sulfur cells

Abstract

The capacity fading of lithium/sulfur (Li/S) cells is one major challenge that has to be overcome for a successful commercialization of this electrochemical storage system. Therefore it is essential to detect the major fading mechanisms for further improvements of this system. In this work, the processes leading to fading are analyzed in terms of a linear four state model and correlated to the distribution of relaxation times calculated with a modified Levenberg-Marquardt algorithm. Additionally, the Warburg impedance and the solution resistance are also obtained by the same algorithm. The detailed analysis of intermediate states during the first cycle gives the distinction between relaxation processes at the sulfur cathode and at the lithium anode. The influence of the polysulfides on the impedance parameters was evaluated using symmetric cells; this yields a good correlation with the results obtained from the first discharge/charge experiment. A fast and a slow capacity fading process are observed for the charge and the discharge during 50 cycles. The fast fading process can be assigned to Faradaic reactions at the lithium anode.

Evaluation of the Effect of Sulfur on the Performance of Nickel/Gadolinium‐Doped Ceria Based Solid Oxide Fuel Cell Anodes

“…Unless stated otherwise, the cells were characterized by using EIS by using an electrochemical workstation (Zahner PP-240 with Thales software) in the frequency range from 100 mHz to 100 kHz with 8points decade À1 .T he amplitude of the current stimulus was chosen to achieve av oltage response not higher than 15 mV.T he DRT was calculated by using am odified Levenberg-Marquardt algorithm adapted from Ref. [68].…”

Quantitative Galvanostatic Intermittent Titration Technique for the Analysis of a Model System with Applications in Lithium−Sulfur Batteries

“…For example, a detailed analysis of impedance measurements of polysulfide solutions with well‐behaved glassy carbon electrodes, complemented with UV‐vis measurements, demonstrated the importance of disproportionation reactions, and the use of this technique to estimate values of the relevant rate constants and diffusion coefficients . Impedance spectroscopy has also been used to evaluate the individual contributions from electrolyte resistance, charge transfer, ion diffusion and electrode surface layers, which in turn has been used to refine mechanistic models of Li−S cells,, as well as to investigate capacity fading . Other experimental techniques used to elucidate redox and diffusion properties in Li−S cells include XAS, in‐operando optical imaging of the temporal and spatial distribution of polysulfides, UV‐Vis spectroscopy, NMR, EPR/ESR,, XRD, Raman, HPLC, and gas evolution, among other electrochemical studies .…”

“…[9] Impedance spectroscopy has also been used to evaluate the individual contributions from electrolyte resistance, charge transfer, ion diffusion and electrode surface layers, [10][11][12][13][14][15] which in turn has been used to refine mechanistic models of LiÀS cells, [16,17] as well as to investigate capacity fading. [18][19][20] Other experimental techniques used to elucidate redox and diffusion properties in LiÀS cells include XAS, [21][22][23][24][25][26][27][28][29][30][31][32] in-operando optical imaging of the temporal and spatial distribution of polysulfides, [33] UV-Vis spectroscopy, [34][35][36][37][38][39][40][41][42] NMR, [43][44][45][46] EPR/ESR, [40,47] XRD, [48][49][50][51][52][53][54]…”

Insights into solid electrolyte interphase formation on alternative anode materials in lithium-ion batteries

“…The distribution of relaxation times (DRT) was analyzed on the basis of impedance data to separate electrochemical processes with different time constants, to help detect processes which might otherwise remain unresolved. The numerical scheme followed a Levenberg-Marquardt algorithm and was already described in detail previously [22]. The measured spectra were transformed with the Z-HIT function of the Zahner Software Thales to ensure that no unwanted artifacts occur due to test duration or drifts in the system.…”