Exploring the nanoscale origin of performance enhancement in Li$_{1.1}$Ni$_{0.35}$Mn$_{0.55}$O$_2$ batteries due to chemical doping

TL;DR

This study demonstrates that chemical doping enhances the performance and stability of Li-rich Mn oxide batteries by improving nanoscale structural compatibility and lithium ion pathways, making them more viable for electric vehicle applications.

Contribution

It reveals how optimized doping profiles at the nanoscale improve structural stability and ion transport in Li-rich Mn oxide cathodes, advancing Co-free lithium-ion battery technology.

Findings

Doping increases initial capacity to 159 mAhg$^{-1}$ and capacity retention to 94.3% after 150 cycles.

Nanoscale analysis shows improved phase compatibility and unobstructed lithium pathways.

Structural stabilization near the surface is observed via advanced electron microscopy techniques.

Abstract

Despite significant potential as energy storage materials for electric vehicles due to their combination of high energy density per unit cost and reduced environmental and ethical concerns, Co-free lithium ion batteries based off layered Mn oxides presently lack the longevity and stability of their Co-containing counterparts. Here, we demonstrate a reduction in this performance gap via chemical doping, with Li$_{1.1}$Ni$_{0.35}$Mn$_{0.55}$O$_2$ achieving an initial discharge capacity of 159 mAhg$^{-1}$ at C/3 rate and a corresponding capacity retention of 94.3% after 150 cycles. We subsequently explore the nanoscale origins of this improvement through a combination of advanced diffraction, spectroscopy, and electron microscopy techniques, finding that optimized doping profiles lead to an improved structural and chemical compatibility between the two constituent sub-phases that characterize the layered Mn oxide system, resulting in the formation of unobstructed lithium ion pathways between them. We also directly observe a structural stabilization effect of the host compound near the surface using aberration corrected scanning transmission electron microscopy and integrated differential phase contrast imaging.