High Energy Density and Long Cycle Life Achieved in Mo-Doped Lini0.5mn1.5o4 Cathode from Dual Enhanced Electronic and Ionic Conductivities

Owing to the inherently low capacity of the LiNi0.5Mn1.5O4 (LNMO) cathode material, its appeal for high-energy applications has progressively diminished. In this study, we extended the operating voltage range to 2-5 V and enhanced the electronic and ionic conductivities through Mo doping, ultimately leading to a significant improvement in both capacity and cycle life. Among the investigated samples, LiNi0.5Mn1.49Mo0.01O4 demonstrated superior electrochemical performance, evidenced by an initial discharge specific capacity of 226.6 mAh g–1 and an energy density of 796 Wh kg–1 at a 0.1C rate. Following 100 charge-discharge cycles, the discharge specific capacity diminished from 209.9 mAh g–1 to 178.8 mAh g–1, with a capacity retention of 85.2%. The exceptional cycling performance can be primarily ascribed to the improved electronic structure, which arises from a narrowed bandgap and an increased number of free electrons near the Fermi level after Mo doping, thereby boosting electronic conductivity. Furthermore, Mo doping results in an elongation of the Li-O bond length, consequently expanding the volume of the LiO4 tetrahedra. This volumetric expansion contributes to an increase in the Li+ diffusion coefficient (DLi+) from 4.726×10–13 cm2 S–1 to 2.112×10–12 cm2 S–1, indicative of augmented Li+ ion conductivity and an ameliorated rate capability of the LNMO cathode material. At a 2C rate, the Mo-doped sample sustained a discharge capacity of 166.6 mAh g–1, in stark contrast to the mere 123 mAh g–1 exhibited by the undoped sample.