Unveiling the vacancy-mediated charge kinetics and capacity fading mechanism in Mn-based cathode for lithium-ion battery

Abstract

In the recent past, Li2MnSiO4 (LMS) has been considered a promising cathode material for high energy density lithium-ion batteries (LIBs). Extraction of the maximum amount of Li from the host LMS and reversibility of Li insertion and extraction is still challenging, probably because of poor conductivity and, thereby, poor Li-kinetics. To improve the Li-diffusion and ionic conductivity, oxygen vacancies (OVs) in pristine LMS (LMS180) have been created, and then their impact on the Li-reactivity of LMS is studied. The quantity of OVs is determined by X-ray photoelectron spectroscopy (XPS) and calculated to be 6.8% in LMS180 heated at 300 ºC in Ar (LMSA300) and ∼ 8.2% in LMS180 heated at 500° C in Ar (LMSA500), subsequently it is supported and validate by the electron paramagnetic response (EPR) and high-resolution transmission electron microscopy (HR-TEM). The best sample, i.e., LMSA500, exhibits a total conductivity of 8.06×10−6 S/cm, resulting in an initial charge capacity of 292 (±5) mAh/g at 10 mA/g. The OVs are found to facilitate the facile lithium-ion movement by providing the lowest migration energy. Furthermore, knowing the impacts of OVs presence in LMS and their effect on Li-diffusion enables us to address traditional capacity fading processes in LMS.