Effect of lithium-ion diffusibility on interfacial resistance of LiCoO2 thin film electrode modified with lithium tungsten oxides

Tetsutaro Hayashi, Takamichi Miyazaki, Yasutaka Matsuda, Naoaki Kuwata, Motoaki Saruwatari, Yuki Furuichi, Koji Kurihara, Ryuichi Kuzuo, Junichi Kawamura

    Research output: Contribution to journalArticlepeer-review

    23 Citations (Scopus)

    Abstract

    To investigate the contribution of lithium-ion diffusibility of lithium tungsten oxides (LWOs) to low interfacial resistance, we fabricate thin-film electrodes of 6Li-enriched LiCoO2 (6LCO) modified with various structure-types of 6Li-enriched LWOs by pulsed laser deposition. The electrodes are subjected to X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and secondary-ion mass spectrometry (SIMS) analyses. XRD reveals that the LWO layers have Li2WO4 structure with rhombohedral and tetragonal symmetries and amorphous states. EIS shows that the lowest interfacial resistance of the positive electrodes is given by the amorphous state, followed in order by the tetragonal and the rhombohedral symmetry, and that the diffusion coefficients of lithium-ions in the electrodes increase in the same order. SIMS demonstrates that the fastest lithium-ion self-diffusibility into the LWOs is found in the amorphous state, followed in order by tetragonal and rhombohedral symmetry. Furthermore, the amorphous state LWO modification shows smooth lithium-ion diffusion between the LWO and LCO layers after the electrochemical test. Conversely, the rhombohedral LWO modification demonstrates congested lithium-ion diffusion between the LWO and LCO layers after the test. Thus, fast lithium-ion self-diffusibility into the LWO-modified LCO contributes to enhancing the diffusion of lithium-ions, resulting in the reduction of interfacial resistance.

    Original languageEnglish
    Pages (from-to)46-53
    Number of pages8
    JournalJournal of Power Sources
    Volume305
    DOIs
    Publication statusPublished - 2016 Feb 15

    Keywords

    • Lithium cobalt oxide
    • Lithium tungsten oxide
    • Lithium-ion diffusibility
    • Low resistance
    • Pulsed laser deposition
    • Secondary-ion mass spectrometry

    ASJC Scopus subject areas

    • Renewable Energy, Sustainability and the Environment
    • Energy Engineering and Power Technology
    • Physical and Theoretical Chemistry
    • Electrical and Electronic Engineering

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