关键词: CuF₂/MoO₃/C复合材料, 转化反应, 电化学阻抗谱, 肖特基接触阻抗

Abstract: Composite electrode of CuF₂/MoO₃/C was fabricated through high energy mechanical milling. The properties of CuF₂/MoO₃/C were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), galvanostatic charge-discharge measurements, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the grain sizes of CuF₂ and MoO₃ after milling were 200 ~ 300 nm, and the initial discharge capacity of CuF₂/MoO₃/C was 647 mAh?g-1 at room temperature and at a current density of 10 mA.g^-1. However, the capacity decayed rapidly in the next cycles. CV curves showed one reduction peak at 2.2 V in the first cycle and another one at 3.2 V in the following cycles. The Nyquist diagram of CuF₂/MoO₃/C electrode consisted of two semicircles and one line. During the discharge process, the high frequency semicircle (HFS) may be associated with not only the Li⁺ migration through the SEI film, but also contact resistance between the CuF₂/MoO₃/C composites and the current collector. The middle frequency semicircle (MFS) should be related to the Schottky contact between CuF₂ and conductive agents, which may be the important feature of such composites materials with big band gap. Besides the low frequency line may be related to the diffusion step. A very large value of charge transfer resistance for the CuF₂/MoO₃/C electrode may induce the rapid decay in capacity.

Key words: CuF2/MoO3/C composite electrode, conversion reactions, electrochemical impedance spectra, Schottky contact impedance