High-Speed voltammetry of Mn-doped LiCoO2 using a microelectrode technique |
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Authors: | Shinichi Waki Kaoru Dokko Takashi Itoh Matsuhiko Nishizawa Takayuki Abe Isamu Uchida |
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Affiliation: | (1) Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Aramaki-Aoba, Aoba-ku, Sendai 980-8579, Japan e-mail: uchida@est.che.tohoku.ac.jp Tel.: +81-22-2177220; Fax: +81-22-2148646, JP |
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Abstract: | The microelectrode technique was applied to investigate the electrochemical properties of LiCo1- x Mn x O2 (x=0, 0.01, 0.05, 0.2, or 0.5) synthesized using the citrate process. From the X-ray diffraction measurements, an expansion of the c-axis and a decrease in the crystal size of the materials were observed on substitution of Mn into LiCoO2. In the electrochemical measurements, the high-speed cyclic voltammogram for the Mn-substituted materials gave one set of peaks at 3.9 V vs. Li/Li+. The apparent chemical diffusion constant (D app) of LiCo0.8Mn0.2O2 obtained from the potential step experiment was 6.4 × 10−8 cm2/s, which is larger than that of LiCoO2. The increase in D app is attributable to the expansion of the c-axis and/or the decrease in the crystal size. In addition, the increase in Mn substitution up to 20% lead to an improvement in the kinetic reversibility and the cycle stability of LiCoO2. Received: 7 June 1999 / Accepted: 25 June 1999 |
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Keywords: | High speed voltammetry Lithium cobalt oxide Manganese substitution Kinetic reversibility Cycle stability |
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