NMC cathode materials: effect of processing parameters on their functional properties

Abstract

Lithium-Nickel-Manganese-Cobalt-Oxide (so-called NMC) based cathode materials have proven to yield enhanced specific capacity and thermal stability thus, can outperform lithium iron phosphate (LFP) cathodes in many areas, particularly in terms of operational voltage in which LFPbased Li-ion batteries (LIBs) can only output voltages below 3.4 V and suffer from high rates of selfdischarge. Within NMC compositions, Nickel provides high energy density and increased storage capacity at lower cost and contributes to the circular economy due to the durability, recyclability and possible second life. However, the majority of degradation mechanisms of Ni-rich NMC-based cathodes are linked to their morphology and crystal structure related mechanisms as well as being dependent on the Ni/Mn/Co ratios. Increased nickel content can result in an increased cation mixing due to the bulk diffusion of Ni2+ causing increased parasitic reactions as the valence of surface Ni increases toward highly reactive Ni4+. Due to the issues with their thermal instability at the fully charged state and insufficient cycle life, researchers are forced to explore approaches to improve these for enhancement of the overall performance of cathodes.