X-ray absorption spectroscopy study of the LixFePO4 cathode during cycling using a novel electrochemical in situ reaction cell.

摘要: The extraction and insertion of lithium in LiFePO4 has been investigated practical Li-ion intercalation electrodes for batteries using Fe K-edge X-ray absorption spectroscopy (XAS). A versatile electrochemical situ reaction cell was utilized, specifically designed long-term experiments on battery during the lithium-extraction/insertion process electrode materials batteries. contained about 7.7 mg a 20 µm-thick Al foil. In order to determine charge compensation mechanism structural perturbations occurring system cycling, fine-structure (XAFS) measurements were conducted at moderate rate typical operating voltages (3.0–4.1 V versus Li/Li+). XAS studies measured initial state (LiFePO4) showed iron be Fe(II) corresponding (0.0 mAh) battery, whereas delithiated (FePO4) found Fe(III) final charged (3 mAh) battery. near-edge structure (XANES) region spectra revealed high-spin configuration two states [Fe(II), d6 Fe(III), d5]. XAFS data analysis confirmed that olivine FePO4 is retained by electrodes, which agreement with diffraction observations these compounds. collected continuously cycling details response cathode Li extraction. These show material retains good short-range leading superior cycling.