Roadblocks in Cation Diffusion Pathways: Implications of Phase Boundaries for Li-Ion Diffusivity in an Intercalation Cathode Material

Abstract

Increasing intercalation of Li-ions brings about distortive structural transformations in several canonical intercalation hosts. Such phase transformations require the energy dissipative creation and motion of dislocations at the interface between the parent lattice and the nucleated Li-rich phase. Phase inhomogeneities within particles and across electrodes give rise to pronounced stress gradients, which can result in capacity fading. How such transformations alter Li-ion diffusivities remains much less explored. In this article, we use layered VO as an intercalation host and examine the structural origins of the evolution of Li-ion diffusivities with phase progression upon electrochemical lithiation. Galvanostatic intermittent titration measurements show a greater than 4 orders of magnitude alteration of Li-ion diffusivity in VO as a function of the extent of lithiation. Pronounced dips in Li-ion diffusivities are correlated with the presence of phase mixtures as determined by Raman spectroscopy and X-ray diffraction, whereas monophasic regimes correspond to the highest Li-ion diffusivity values measured within this range. First-principles density functional theory calculations confirm that the variations in Li-ion diffusivity do not stem from intrinsic differences in diffusion pathways across the different lithiated VO phases, which despite differences in the local coordination environments of Li-ions show comparable migration barriers. Scanning transmission X-ray microscopy measurements indicate the stabilization of distinct domains reflecting the phase coexistence of multiple lithiated phases within individual actively intercalating particles. The results thus provide fundamental insight into the considerable ion transport penalties incurred as a result of phase boundaries formed within actively intercalating particles. The combination of electrochemical studies with ensemble structural characterization and single-particle X-ray imaging of phase boundaries demonstrates the profound impact of interfacial phenomena on macroscopic electrode properties.

Transport properties of electron small polarons in a V2O5 cathode of Li-ion batteries: a computational study

“…26,39 In addition, several experimental and computational works have extensively been studied and reported evolution of atomic and electronic structures of various V 2 O 5 phases upon lithiation in the context of cathode materials for Li-ion batteries. 26,27,[38][39][40][41] For the sake of completeness, in this work, we re-examined the atomic and electronic structures of polaron formation in V 2 O 5 to ensure the validity of our computations. We considered the formation of an electron polaron in two different situations, i.e.…”

“…31 In addition, at higher Li concentration, Li x V 2 O 5 undergoes phase transformation where the limitations of transport kinetics were identied for ion diffusion at the phase boundaries. 40…”

“…Such creation of phase boundaries has been found to greatly diminish Li-ion diffusivity at the V 2 O 5 cathode. 40 Several strategies have been suggested to boost the electrochemical kinetics of the V 2 O 5 cathode. For instance, to avoid the slow diffusion kinetics at the interface, one could operate the cathode in the voltage range where the material maintains its original phase.…”

Lithium–Lanthanide Bimetallic Metal–Organic Frameworks towards Negative Electrode Materials for Lithium‐Ion Batteries

“…Althoughc apacity fading occurredd uring cycling, the high specific capacity of CeLipma still providesapromising choice for novel electrode materials. Compared with other electrodes assembled from rare-earth-based materials, the reversible capacityo fC eLipma is highert han those of CeO 2 @C [47] and Tb 2 (H 2 dobdc) 3 (dmf) 4 [26] under similarc onditions, which is even bettert han that of certain compounds without rare-earth metals, [40,41,45] suggesting that rare-earth-based compounds as electrode materials deserve more in-depthstudy (Table 3).…”

“…With the diminishing reserves of traditional fossil fuels,l ithiumion batteries (LIBs) have attractedw orldwidea ttention due to their highe nergy and powerd ensity,l ongc ycle life, low weight, and flexibility for the manufacture of various shapes and sizes. [1][2][3][4][5] Simply,LIBs are ag reen power system, potentially used in energy gass torage, optics, electricity,m agnetism, biomedical, and other fields. [6][7][8] LIBs, whicha re one of the most promisinge nergy-storaged evices, have been widely used in portable devices,e lectric vehicles, hybrid electric vehicles, and so forth.…”