Pillared layered Li 1−2 xCa xCoO 2 cathode materials obtained by cationic exchange under hydrothermal conditions

Abstract

A simple method has been employed to prepare pillared layered Li 1−2 x Ca x CoO 2 cathode materials by cationic exchange under hydrothermal conditions. The synthesized materials were characterized by means of X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), field emission scanning electron microscope (FE-SEM) and galvanostatic charge–discharge cycling. The XRD data of the products show that they are single phases and retain the layered α-NaFeO 2 type structure. The FE-SEM images of the materials prepared by hydrothermal method show uniform small particles, and the particle size of the materials is about 200 nm. The initial discharge specific capacities of layered LiCoO 2 and pillared layered Li 0.946Ca 0.027CoO 2 cathode materials calcined at 800 °C for 5 h within the potential range of 3.0–4.3 V (vs. Li +/Li) are 144.6 and 142.3 mAh g −1, respectively, and both materials retain good charge–discharge cycling performance. However, with increasing upper cutoff voltage, the pillar effect of Ca 2+ in Li 1−2 x Ca x CoO 2 becomes more significant. The pillared layered Li 0.946Ca 0.027CoO 2 has a higher capacity with an initial discharge specific capacity of 177.9 and 215.8 mAh g −1 within the potential range of 3.0–4.5 and 4.7 V (vs. Li +/Li), respectively, and retains good charge–discharge cycling performance.