Exploring the Nanoscale Origin of Performance Enhancement in Li_(1.1)Ni_(0.35)Mn_(0.55)O_2 Batteries Due to Chemical Doping

摘要

Despite significant potential as energy storage materials for electric vehiclesdue to their combination of high energy density per unit cost and reducedenvironmental and ethical concerns, Co-free lithium ion batteries based on layeredMn oxides presently lack the longevity and stability of their Co-containingcounterparts. Here, a reduction in this performance gap is demonstrated viachemical doping, with Li_(1.1)Ni_(0.35)Mn_(0.54)Al_(0.01)O_2 achieving an initial dischargecapacity of 159 mAhg~(?1) at C/3 rate and a corresponding capacity retentionof 94.3 after 150 cycles. The nanoscale origins of this improvement aresubsequently explored through a combination of advanced diffraction, spectroscopy,and electron microscopy techniques, finding that optimized dopingprofiles lead to an improved structural and chemical compatibility between thetwo constituent sub-phases that characterize the layered Mn oxide system,resulting in the formation of unobstructed lithium ion pathways betweenthem. A structural stabilization effect of the host compound is also directlyobserved near the surface using aberration corrected scanning transmissionelectron microscopy and integrated differential phase contrast imaging.