Thermodynamic/Electrochemical Description of High-Voltage Spinels for Lithium-Ion Batteries

Abstract

High-voltage (HV) spinels obtained by partially substituting Mn with other elements in LiMn 2 O 4 are promising cathode materials for lithium-ion batteries (LIBs) due to their superior energy capacities and recyclability. The improved performance of HV spinels comes from the appearance of multi voltage plateaus without phase transformation during lithiation/delithiation process. To optimize the doping elements is one significant routine to develop new cathode materials. However, it is difficult to investigate HV spinels with multi doping elements due to increased variables. For the first time, we investigate the typical HV spinel, Li Ni , Mn 2 O 4 using one single thermodynamic model with Compound Energy Formalism (CEF), i.e., Va , Li + 1 Li + , Ni 2 + , Ni 4 + , Mn 3 + , Mn 4 + 2 O 2 − 4 and described Ni substitution of Mn as well as lithiation/delithiation behaviours. Both the high voltage (around 4.7 V) and low voltage (around 4.1 V) plateaus of the Li-Ni-Mn-O spinel cathodes are predicted by correctly describing competition between Mn 3 + / Mn 4 + and Ni 2 + / Ni 4 + redox pairs. Meanwhile, we have successfully modelled the key property parameters including the voltage profile, energy density, stability, and cyclability. The presented design scheme is based on the superior cell performance compared to the widely studied LiNi 0.5 Mn 1.5 O 4 , which results in the slightly Li-rich HV spinel Li 1 + x Ni 0.5 Mn 1.5 − x O 4 because of higher energy density and improved cyclability. The here adopted research strategy enables efficient design of the new-generation multi-doped HV spinel Li M , Mn 2 O 4 (M = Li, Al, Co, Cr, Cu, Mg, Fe, Ni, Zn, etc.).