Probing the Operating Voltage and Structural Transitions in Li-Mn-O Layered-Spinel Composite Nanoarchitectures during the Discharge Process.

Abstract

Li-Mn-O layered-spinel (LS) composite is one of the utmost promising cathode materials for advancing lithium-ion batteries, which are lacking in comparison to technological advancements. The currently used cathode materials are one of the limiting factors in realising the envisaged affordable, durable, and safe rechargeable lithium-ion batteries. Their limitations include capacity fading transpiring during cycling, inherent low operational capacities, safety issues due to thermal instabilities, and high cost which inhibit their full utilisation in large scale systems. The LS composite demonstrates enhanced electrochemical properties owing to the synergism of the layered and spinel components. In particular, the 0.7Li2MnO3.0.3Li4Mn5O12 composite, which has demonstrated a higher specific capacity, >250 mAh/g. Recent studies have focused mainly on enhancing the specific capacity of LS composites. However, there is limited knowledge of the structural changes that take place during the discharge process and how they affect the working voltage of the LS composite cathode material. Li-Mn-O LS composites indicating different stages of the discharge process have been generated using the molecular dynamics simulated amorphisation and recrystallisation method, which utilises empirical interatomic potentials. Different structural features of the LS composites in all significant stages of the discharge process were visualised and captured. X-ray diffraction patterns (XRDs) and radial distribution functions were used to characterise the formed layered and spinel components of the LS blend nanoparticles. Moreover, their average voltages were also computed using the linear scaling density functional theory code.