Effect of Magnesium Doping on the Structural Stability of Layered Linio2 Based Cathode Materials.

Abstract

In rechargeable lithium batteries, nickel is employed in the form of oxide in which lithium ions are inserted into its crystal structure to form layered nickel oxide i.e., LiNiO 2 . The objective of this paper is to understand the effects of substitution of magnesium on the structural stability in the layered intercalation compounds. The compounds LiNiO 2 and LiNi 0.75 Mg 0.25 O 2 are synthesized by a solid state reaction method under the flow of air at 800 °C for 24 hours. The influence of doping Mg on structure, morphology and bonding nature of cathode materials are investigated systematically. From the x-ray diffraction (XRD) data, the intensity versus diffraction angle peak indicated that the compound crystallized as a rhombohedral system (space group m R3 ). The lattice constants and crystallite sizes were computed from XRD data. The particle morphology of the compound was observed using a field effect scanning electron microscope (FESEM). The FT-IR spectroscopic data of LiNiO 2 revealed the local structure of the oxide lattice constituted by LiO 6 and NiO 6 octahedra.Copy Right, IJAR, 2016,. All rights reserved. …………………………………………………………………………………………………….... Introduction:-Over the last two decades, intensive research is going on to improve the overall performance of lithium ion batteries. The main focus has been in search of the alternative cathode materials, apart from the regular components of battery mechanisms. For the cathode materials, every system has its own advantages and disadvantages. The LiCoO 2 is a well known cathode material for rechargeable lithium ion batteries [1]. However, due to its high cost and toxicity, there has been a continuous demand during the last few years to develop alternative cathode materials which would be environmentally friendly and cost effective [2][3]. Metal based LiNiO 2 , LiMn 2 O 4 and olivine type LiFePO 4 are promising materials for future to substitute LiCoO2. The LiNiO 2 is cheaper and less toxic compared to LiCoO 2 [4]. It delivers a larger reversible capacity with a comparable life-cycle. It is considered to be one of the best cathode materials for Lithium ion cells. The electrochemical properties of cathodes based on LiNiO 2 are good. The difficulty in synthesizing stoichiometric LiNiO 2 is also due to the loss of lithium from the host structure during high temperature calcinations because of the high vapor pressure of lithium [5][6], thus leading to the formation of nonstoichiometric structure. However, its synthesis requires special care to obtain good and reproducible performances.