Impact of Isovalent and Aliovalent Doping on Li ion Storage Kinetics of Li3V2 xMx PO4 3

Abstract

Commercialising the lithium-ion battery technology in transportation has become an indispensable necessity of the twenty first century, where pollution and climate change are a major concern. Mass marketisation of battery-driven, fossil fuel-free vehicles is a crucial strategy proposed to combat the climate change crisis that the world is facing today. The safety aspects of the lithium-ion battery driven electric vehicles deserve closer attention, and this prima facie demands a shift in the focus of the scientific research community from the fierce search for high-energy, high-power density electrode materials to developing better performing battery materials with guaranteed intrinsic safety. In this context, cathode materials with phosphate framework deserves remarkable attention among the innumerable positive electrode materials predicted for lithium-ion battery applications of the future. Among them, Lithium Vanadium Phosphate [Li3V2(PO4)3] is particularly attractive due to its potentially safe electrolyte operating voltage window of 3V - 4.8V, high theoretical capacity of 197 mAh/g, a high average plateau potential of 4V, theoretically possible energy density of ~800 Wh/kg and minimum volume expansion. The primary disadvantages of LVP lies in its poor electronic conductivity due to the phosphate ligand group induced polaron electron movement inside the crystal structure and poor ionic conductivity leading to sluggish kinetics during the cell cycling. Doping has been attempted extensively as a strategy to address the conductivity issues in LVP. Though there has been extensive progress made in the doping research in LVP so far, there has not been a comprehensive understanding made through the fundamental aspects defining the inherent changes occurring in the structure as a result of doping. Till date, there have not been a distinct pattern identified in the doping strategies that demarcate why some ions improve the performance in terms of capacity or rate capability while some similar ones ...