A Comprehensive Investigation on Nano Scale Engineering for Surface Phase Stabilization in Licoo2 upon Extended Delithiation

Abstract

Lithium ion batteries (LIB) governs the electronic market with its remarkable properties of high reversible capacity, high energy density and long cycle life. Lithium cobalt oxide (LiCoO2- LCO) is the first ever cathode material commercialized in the rechargeable LIB industry and still it continues it race as a prominent cathode in wide range of applications owing to its fascinating electrochemical properties. Despite of these advantages, practical capacity of the material is limited to 140 mAh/g with a charge cutoff limit of 4.2 V, taking into account of the structural instability beyond that cut-off. Modern society relies more on electronic devices and that urges the need of high energy and power density batteries. More recently, researchers paid significant interest in the extension of charge cutoff voltage of the material for the upgradation of its reversible capacity and energy density. Multiple strategies were implemented by various groups across the globe for the development of high voltage LCO with a stable structure. From the literatures reported for high voltage LCO (and#8805; 4.5 V), we observed some gaps between the present state of art and the future high power applications. The major gaps observed are as follows: (a) among different surface coating agents adopted for LCO, there observed limited reports for high temperature performance (HT) studies done with metal oxide/fluorides coatings at high rates, (b) lack of low temperature (LT) cycling studies, (c) nonexistence of high rate performance at 4.8 V and (d) a comprehensive understanding of the effect of coating chemistry and their thickness variations. Wide climatic operation is a critical parameter that has to be considered in view of commercial applications. The present thesis focus on the development of a high voltage LCO that offers high rate capacity and high energy density with a well stabilized structure at and#8805;4.5 V. Surface engineering strategy adopted in the work resulted in the accomplishment of a structurally stable, fast charging high voltage...