Synthesis and characterization of Al and Zr-dual-doped lithium cobalt oxide cathode for Li-ion batteries using a facile hydrothermal approach

Abstract

Here, we have studied synthesis and characterization (structural, morphological, and electrochemical) of pure and Al-Zr dual-doped Li-rich LiCoO2 (LCO) cathode materials for lithium-ion batteries (LIBs). A solution-based hydrothermal approach was utilized to synthesize the “Li[Li0.1Co0.9−x-yZrxAly]O2” and others. The desired phase of Li-rich LCO was obtained at a sintering temperature (800 °C) which is relatively lower compared to most of the previously reported solid-state methods, which reveals the significance of the conducted study. Various characterization tools e.g., X-ray diffraction (XRD), Field-emission scanning electron microscope (FESEM), Fourier-transform infrared spectroscopy (FTIR), and Energy Dispersive X-ray spectroscopy (EDS) were employed to assess the metal-doping effect on structural and morphological features of as-prepared cathode materials. Additionally, the electrochemical performance of the cathode materials was examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Moving forward, XRD has confirmed the formation of hexagonal layered α-NaFeO2 iso-structure with the preferred orientation along (1 0 1) plane. Moreover, the sharp XRD pattern demonstrates the harmless nature of doping toward crystallinity and structural stability. Rietveld refinement analysis has demonstrated an initial decrease followed by an increase in cell volume, indicating the successful intrusion of Al & Zr on Co-sites. Upon doping, the particle size has been shifted from micro to nanoparticles, as indicated by FESEM images. The reduction in particle size will increase the effective reaction area and subsequently enhance overall electrochemical performance. The optimum electrochemical performance was observed in sample Li[Li0.1Co0.9–0.015–0.085Zr0.015Al0.085]O2 with a working potential of 4.18 V, anodic current (0.764 mA), cathodic current (0.706 mA), the specific capacity of 185 mAh g−1 with capacity retention of 91% after 100 cycles at a scan rate of 0.1 C. With further increasing Zr content over 1.5%, structural disruption occurs which affects the reaction's kinetics and eventually reduces cathode performance.