Solid-state electrochemical kinetics of Li-ion intercalation into Li{sub 1{minus}x}CoO{sub 2}: Simultaneous application of electroanalytical techniques SSCV, PITT, and EIS
- Bar-Ilan Univ., Ramat-Gan (Israel). Dept. of Chemistry
- Merck KGaA, Darmstadt (Germany)
The electroanalytical behavior of thin Li{sub 1{minus}x}CoO{sub 2} electrodes is elucidated by the simultaneous application of three electroanalytical techniques: slow-scan-rate cyclic voltammetry (SSCV), potentiostatic intermittent titration technique, and electrochemical impedance spectroscopy. The data were treated within the framework of a simple model expressed by a Frumkin-type sorption isotherm. The experimental SSCV curves were well described by an equation combining such an isotherm with the Butler-Volmer equation for slow interfacial Li-ion transfer. The apparent attraction constant was {minus}4.2, which is characteristic of a quasi-equilibrium, first-order phase transition. Impedance spectra reflected a process with the following steps: Li{sup +} ion migration in solution, Li{sup +} ion migration through surface films, strongly potential-dependent charge-transfer resistance, solid-state Li{sup +} diffusion, and accumulation of the intercalants into the host materials. An excellent fit was found between these spectra and an equivalent circuit, including a Voigt-type analog (Li{sup +} migration through multilayer surface films and charge transfer) in series with a finite-length Warburg-type element (Li{sup +} solid-state diffusion), and a capacitor (Li accumulation). In this paper, the authors compare the solid-state diffusion time constants and the differential intercalation capacities obtained by the three electroanalytical techniques.
- OSTI ID:
- 345313
- Journal Information:
- Journal of the Electrochemical Society, Vol. 146, Issue 4; Other Information: PBD: Apr 1999
- Country of Publication:
- United States
- Language:
- English
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