Structural, electrical and electrochemical characterization of hybrid morphological LiNi0.5Mn1.5O4 cathode material

Abstract

Spinel LiNi0.5Mn1.5O4 (LNMO) cathode are effectively obtained by one-pot hydrothermal synthesis. Scanning electron microscopy (SEM) reveals the hybrid morphological of LNMO, featuring cotton-like structures (400–800 nm) and rod-like structures (90–150 nm). The equivalent circuit well describes the Nyquist plot to separate the grain and grain boundary effects. According to the Maxwell-Wagner model, the complex permittivity confirms non-homogenous layers' existence; highly conducting grains and poorly conducting grain boundaries. Non-overlapping polar tunneling (NSPT) and correlated barrier hopping (CBH) are two responsible models for the conduction mechanism at low and high temperatures. Further, identical activation energy values are observed for hopping frequency, and peak frequency from normalized parameters Z’’/Z’’ max and M’’/M’’ max, suggesting Li+ ions are the dominant charge carriers. The LNMO/Li cell delivers higher discharge capacity than commercial LNMO/Li cell from prior study, credits from the bridging features between rod-like and cotton-like particles.