Sc-doping induced cation-disorder in LiNi0.5Mn1.5O4 spinel leading to improved electrochemical performance as cathode in lithium ion batteries

Abstract

Ni/Mn disordered LiNi0.5Mn1.5O4 spinel is the most promising cathode material for lithium ion batteries due to its high energy and power densities. However, the Ni/Mn disorder coupled with high Mn3+ content and concomitant formations of NiO/LiyNi1-yO impurities deteriorate its electrochemical performances. To overcome this issue, Sc-doped disordered spinel LiNi0.5Mn1.44Sc0.06O4 without NiO/LiyNi1-yO impurities has been synthesized. Infrared spectroscopy, magnetic measurements and cyclic voltammetry results reveal the increase in Ni/Mn disordering of LiNi0.5Mn1.44Sc0.06O4 than pristine spinel which decreases the charge transfer resistance and enhances the electrochemical performances. The XPS spectrum of LiNi0.5Mn1.44Sc0.06O4 exhibits Sc2p3/2 (402.3 eV) and Sc2p1/2 (406.5 eV) bands confirming the presence of Sc3+ in the spinel lattice. Sc-doped spinel delivers an initial discharge capacity 131 mAhg−1 with 88% columbic efficiency at 0.1C rate. Under similar condition, the undoped spinel yields only 123 mAhg−1 with 81% columbic efficiency. In addition, cycling stability of the doped spinel has increased dramatically with increase in the C-rate. At 5C, it exhibits a specific capacity of 102 mAhg−1 with 98% capacity retention even after 1000 cycles. Furthermore, it demonstrates excellent rate capability due to enhanced lithium-ion diffusion kinetics. The improved performance of the spinel can be attributed to the stabilization of the cation disordered structure. Thus, the Sc-doped spinel could be a potential cathode material for lithium ion batteries for electric vehicle applications.