Enhanced electrochemical performance of spinel LiNi 0.5 Mn 1.5 O 4 for Li-ion batteries with moderate Mn 3+ concentration and nanosized thin Al 2 O 3 coating

In this paper, Al2O3 was selected as a modifying material to improve the electrochemical performance of spinel LiNi0.5Mn1.5O4 (LNMO) by a simple wet chemical process. SEM and TEM analyses indicated that the Al2O3 was coated on the surface of LNMO surface with the thickness of ~ 10 nm. Meanwhile, XRD, Raman, and XPS analyses indicated that the introduction of Al2O3 had a slight change in LNMO structure from disordered phase to ordered phase, with the decrease of Mn3+ concentration. The optimized LNMO (LNMO@AO-1 wt%) delivered specific capacities of 129 and 109 mA h g−1 at 1 and 20 C rates, respectively. At the 1 C cycling rate, capacity retention of 96% was obtained after 300 cycles, much better than pristine LNMO of 86%. The remarkable performance was attributed to the introduction of Al2O3 that can not only form inert coating layer to isolate the contact between electrolyte and electrode surface, but also reduce the Mn3+ concentration in materials appropriately, thus alleviating the disproportional reaction and Jahn–Teller distortion effect.