Comparing Cycling Characteristics of Symmetric Lithium-Polymer-Lithium Cells with Theoretical Predictions

Abstract

We develop a model based on concentrated solution theory for predicting the cycling characteristics of a lithium-polymer-lithium symmetric cell containing an electrolyte with known transport properties. The electrolytes used in this study are mixtures of polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt, prepared over a wide range of salt concentrations. The transport properties of PEO/LiTFSI previously reported in the literature are used as inputs for our model. We calculate salt concentration and potential profiles, which develop in these electrolytes under a constant dc polarization, as a function of current density, electrolyte thickness, and salt concentration. These profiles are nonlinear at steady-state due to the strong concentration dependence of the transport properties of this electrolyte. The effect of this nonlinearity on limiting current is demonstrated. Cycling characteristics of a series of lithium symmetric cells were measured to test the validity of our model, without resorting to any adjustable parameters. The time-dependence and steadystate value of the potential measured during cycling experiments were in excellent agreement with model predictions.

Measurement of Three Transport Coefficients and the Thermodynamic Factor in Block Copolymer Electrolytes with Different Morphologies

“…Complete electrochemical characterization of ion transport enables prediction of timedependent salt concentration and potential gradients across a battery electrolyte during dc polarization 31,32 . A desirable electrolyte will have small salt concentration and potential gradients within the electrolyte at large current densities.…”

Wetting Phenomena and their Effect on the Electrochemical Performance of Surface‐Tailored Lithium Metal Electrodes in Contact with Cross‐linked Polymeric Electrolytes

“…As an ext step,t he cell voltage (E)r esponse of Li metal electrodes during electrodeposition was correlated with the wettability properties of the PEs.W ed escribe this response based on wettability-dependent electrochemical interfaces in PE-based LMBs.F ollowing Figure 4a,t he response of E to am oderate constant current density ( % 0.1 mA cm À2 for the observed systems) consists of ap otential drop deducing Ohmslaw (h Ohm )( Figure S11) and an arc-shaped overpotential response (h arc )b efore reaching as teady-state potential (E steady-state ). [53,54] When aconstant current density j is applied, h Ohm evolves immediately at av ery short time scale (! seconds), while h arc arises within seconds and minutes, and E steady-state is typically reached within minutes or some-times hours (strongly depending on the observed system).…”

Benetzungsvorgänge und ihr Einfluss auf die elektrochemischen Eigenschaften von oberflächenangepassten Lithium‐Metall‐Elektroden in Kontakt mit quervernetzten Polymer‐Elektrolyten

“…Gemäß Abbildung a zeigt E nach Anlegen einer moderaten, konstanten Stromdichte (≈0,1 mA cm −2 ) einen Spannungsabfall, der sich aus dem Ohm'schen Gesetz ( η Ohm ) ableiten lässt (Abbildung S11). Hierbei zeigt das Verhalten eine Kreisbogen‐förmige Überspannungsantwort ( η arc ) bevor das Gleichgewichtspotential ( E steady‐state ) erreicht wird . Wenn eine konstante Stromdichte j angelegt wird, verändert sich η Ohm augenblicklich in einer sehr kurzen Zeitspanne (≪ Sekunden), während η arc innerhalb von Sekunden bis Minuten ansteigt und E steady‐state typischerweise innerhalb von Minuten oder manchmal erst nach Stunden erreicht ist (stark abhängig vom untersuchten System) .…”