Nanoconfinement geometry of pillared V2O5 determines electrochemical ion intercalation mechanism and diffusion pathway

Improving electrochemical ion intercalation capacity and kinetics in layered host materials is a critical challenge to further develop lithium-ion batteries, as well as emerging cell chemistries based on ions beyond lithium. Modification of the nanoconfined interlayer space within host materials by synthetic pillaring approaches has emerged as a promising strategy, however, the resulting structural properties of host materials, host-pillar interaction, as well as evolving structure-functionality relations remain poorly understood. Herein, a series of bilayered V2O5 host materials pillared with alkyldiamine molecules of different lengths is systematically studied, resulting in tunable nanoconfinement geometry with interlayer spacings in the range of 1.0-1.9 nm. The electrochemical Li+ intercalation capacity is increased from approx. 1 to 1.5 Li+ per V2O5 in expanded host materials, and the intercalation kinetics improve with larger expansion. Operando X-ray diffraction reveals a transition of the charge storage mechanism from solid-solution Li+ intercalation in V2O5 hosts with small and medium interlayer spacings, to cointercalation of Li+ and solvent in V2O5 with the largest interlayer spacing. Density functional theory reveals a transition in Li+ diffusion pathways from 1D to 2D diffusional networks for expanded interlayers. The work reveals the impact of nanoconfinement geometry within bilayered V2O5 on the resulting Li+ intercalation properties, providing insights into both the microstructure and related functionality of pillared materials.