Nanoconfinement Geometry of Pillared V ₂ O ₅ Determines Electrochemical Ion Intercalation Mechanisms, Storage Sites, and Diffusion Pathways

High Resolution Image Download MS PowerPoint Slide Improving the 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 nanoconfining 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 interactions as well as associated electrochemical mechanisms remain poorly understood. Herein, we systematically study a series of bilayered V 2 O 5 host materials pillared with alkyldiamines of different lengths, resulting in tunable nanoconfinement geometries with interlayer spacings in the range of 1.0–1.9 nm. The electrochemical Li + intercalation capacity is increased from approximately 1.0 to 1.5 Li + per V 2 O 5 in expanded host materials due to the stabilization of new storage sites. The intercalation kinetics improve with expansion due to a transition in Li + diffusion pathways from 1D to 2D diffusional networks. Operando X-ray diffraction reveals a transition of the intercalation mechanism from solid-solution Li + intercalation in V 2 O 5 hosts with small and medium interlayer spacings to solvent cointercalation in V 2 O 5 with the largest interlayer spacing. The work systematically demonstrates the impact of nanoconfinement geometry within bilayered V 2 O 5 on the resulting Li + intercalation metrics and mechanisms, providing insights into both the microstructure and associated electrochemistry of pillared materials.