Electrochemical impedance study of Li-ion insertion into mesocarbon microbead single particle electrode: Part I. Graphitized carbon

• Published in: Electrochimica acta 2001-12, Vol.47 (6), p.885-890
• Main Authors: Umeda, M, Dokko, K, Fujita, Y, Mohamedi, M, Uchida, I, Selman, J.R
• Format: Article
• Language: English
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Graphitized carbon; Lithium batteries; Microelectrode; Single particle; Solid electrolyte interphase
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/S0013-4686(01)00799-X

Li-ion insertion and extraction were investigated by electrochemical impedance spectroscopy (EIS) on a single particle mesocarbon microbead (MCMB) (heat-treated at 2800 °C) of 30 μm diameter in 1 M LiClO 4/propylene carbonate+ethylene carbonate solution. The impedance spectra were modeled using an equivalent circuit comprising: (i) Li-ion conduction in the solid electrolyte interphase (SEI) film. (ii) Two charge transfer processes related to the particle/SEI interface, and the SEI/electrolyte interface. (iii) A semi-infinite Warburg-type element, reflecting solid state Li-ion diffusion. (iv) An intercalation capacitance reflecting the accumulation of lithium into the particle. The resistance for Li-ion conduction in the solid electrolyte interphase (SEI) film was found to be independent of the potential. On the other hand, the charge transfer resistance decreased/increased monotonously when the electrode potential shifted to cathodic/anodic direction. This behavior is due to an activation process. The apparent chemical diffusion coefficient of lithium in the MCMB particle was found to be within the range 10 −6–10 −10 cm 2 s −1, varying as a function of electrode potential with minima at the potentials corresponding to the voltammetric peaks.