Polaron-Assisted Charge Transport in Li-Ion Battery Anode Materials

Abstract

Lithium-ion batteries are without a doubt a key technology in the coming energy revolution. It is thus all the more surprising that one of the more prevalent Li battery anode materials, reduced lithium titanium oxide (LTO, Li4Ti5O12), is still poorly understood on a microscopic level. While recent theoretical and experimental evidence suggests that a polaron hopping mechanism is responsible for the increased electronic conductivity of reduced LTO, no such explanation exists for the concurrent improvements to the ionic mobility. In this computational study, we show that the presence of polaronic Ti3+ centers can indeed lead to a significant lowering of Li hopping barriers in both bulk and surface reduced LTO. For the latter, we find a reduced barrier height of roughly 40 meV compared to that of our pristine reference. This is in accordance with experimental findings showing that lithium-ion diffusion in reduced LTO is twice as high as that for pristine LTO. Finally, we show thatin accordance with experimental observationspolaron formation upon lithiation of LTO leads to a similar behavior. Altogether, our analysis hints at a correlated movement of Li ions and polarons, highlighting LTO’s potential for rational defect engineering.

Enhancing V2O5 Cathode Performance through Heterostructure Engineering with the Ti3C2O2 MXene: A Computational Study

“…It destabilizes the formation of polarons at the V 2 O 5 interface. Such less stable polarons exhibit a smaller electron–lattice interaction, which could improve charge transport kinetics at the interface . The details of these calculations are discussed as follows.…”

Fast carrier diffusion via synergistic effects between lithium-ions and polarons in rutile TiO2

“…47 Oxygen deficiency is associated with the presence of V O 2+ . 48 Hightemperature thermal annealing, electron bombardment, and UV irradiation under oxygen-deficient or vacuum conditions also generate oxygen defects. 26,49 Qiu et al have found that the hydrogenation process causes crystalline dislocation and produces V O 2+ throughout the bulk and surface of the rutile TiO 2 .…”

Computational screening and descriptors for the ion mobility in energy storage materials

“…Several additional features influencing ion mobility have been discussed in the literature, including lattice dynamics, phonon frequencies, and amplitudes [3,[15][16][17]. The polarizability of atoms, categorized as a chemical feature, has also been suggested as a potential correlate to ion migration [18,19]. The crystalline lattice framework and structural features can play a role as well, with coordination geometries enhancing cation site stability and increasing migration barriers [20,21].…”