Microscopic electrostatic funnel in nanowire-supported island CuGeO₃/VO₂ heterostructures for high-rate lithium storage.

Ternary copper germanate (CuGeO₃) is a promising high-capacity anode for lithium-ion batteries, yet its practical application is limited by sluggish interfacial reaction kinetics and poor intrinsic conductivity. Herein, a nanowire-supported island CuGeO₃/VO₂ heterostructure was constructed through sequential hydrothermal growth and reactive magnetron sputtering. By regulating the sputtering duration, well-dispersed VO₂ nanoislands were obtained on CuGeO₃ nanowires while preserving exposed CuGeO₃ surface regions. Experimental characterization and density functional theory calculations indicate pronounced interfacial charge redistribution and a spatially nonuniform electrostatic potential landscape around the discrete VO₂ domains. Unlike a conventional planar built-in electric field, the island-like configuration introduces both interfacial and lateral potential variations, forming the proposed microscopic electrostatic funnel that is favorable for Li+ redistribution toward accessible surface and interfacial sites. Climbing-image nudged elastic band (CI-NEB) calculations and galvanostatic intermittent titration technique (GITT) measurements further show more favorable Li migration energetics and enhanced apparent Li+ diffusion kinetics in the heterostructure. Meanwhile, the increased electronic states near the Fermi level facilitate interfacial electron transport. Benefiting from the combined improvement in ion and electron kinetics, CuGeO₃/VO₂ delivers a reversible capacity of 980 mAh g-1 after 200 cycles at 0.1 A g-1 and maintains approximately 737 mAh g-1 at 1.0 A g-1. These results demonstrate the potential of discrete island-like heterointerfaces for regulating local electrostatic environments and improving lithium-storage kinetics in germanium-based oxide anodes.