Improving Li-Ion Anodes with Systematic Elemental Doping in Titanium Niobate

Lithium-ion batteries for high-power
applications have become an
increasingly important area of development as these devices have been
used in implantable medical devices, where extreme safety and long
lifetimes are essential. TiNb2O7 has emerged
as a promising candidate to replace the current industrial standard
Li4Ti5O12 as a safe high-power anode.
In this study, we use combinatorial methods to screen the effects
of 52 different dopants (M) in the composition (TiNb2)0.98M0.06O7 with 52 unique elemental
dopants. The materials were studied with high throughput by X-ray
diffraction and cyclic voltammetry to reveal the performance of the
doped materials. Structural analysis revealed a change in the lattice
parameters dependent on the substituent present, and some extremely
large dopants were able to partially substitute into the materials.
Several doped materials, particularly with large dopants, show excellent
discharge capacities of 326.7 mAh g–1 at room temperature,
an improvement of over 20% over the undoped material despite moderate
doping levels (2% of the metals). Many of the doped TNO samples show
excellent extended cycling, especially at 37 °C. The dramatic
improvements with the addition of large dopants (most of which are
electrochemically inactive) are attributed to distortions in the local
structure improving the Li diffusion paths, thereby enabling higher
capacities, and establish a new design principle in optimizing these
safe anodes.