High energy density batteries are essential for portable electronic devices e.g. Laptops, mobile phones, iPads, toy etc. Besides this, high energy density batteries are also required for power tools and hybrid electric vehicles. Commercially available lead-acid batteries are toxic and have low energy density and not suitable for electronic devices. Advanced Li-ion batteries possess high specific energy as compared to existing rechargeable battery technologies. Commercially available Li ion rechargeable batteries having LiCoO₂ as cathode materials are toxic and expensive due to the presence of cobalt. Additional disadvantage of LiCoO₂ based batteries is their low operating voltage (3 V), which restricts their application for hybrid electric vehicles and power tools. It has already been reported that the charge-discharge characteristics and cycleability of LiMn₂O₄ can be improved by substituting the Mn³⁺ ion with transition metals e.g. Cr, Co, Ni, Cu  etc. To increase the energy density of the Li ion rechargeable batteries we will be exploring the cathode materials, working in higher operating voltage (~5V) range.

We have synthesized LiMn_2-xFe_xO₄ cathode materials for Li ion rechargeable batteries. The concentration of Fe varies from 0.1 to 0.5 with an increment of 0.1. The cathode materials were synthesized by sol-gel method and calcined at various temperature in the range of 800 ^oC to 950 ^oC. The synthesized materials were physically characterized by X-ray diffraction (XRD), differential thermal scanning calorimetry (DSC), micro-Raman spectroscopy and scanning electron microscopy.  We obtained phase pure Fd3m structure in all synthesized compounds. The electrochemical characterization were carried out in a coin cell configuration using cyclic voltammetry, charge-discharge characteristics, impedance spectroscopy and cycleability. Cyclic voltametric studies reveal the reversible electrochemical properties of LiMn_2-xFe_xO₄ cathode materials. The detailed results and discussion on physical and electrochemical properties of LiMn_2-xFe_xO₄ cathode materials will be presented in the ECS 229^th meeting.