Experimental and Computational Insights into Built‐In Electric Field at Bronze TiO ₂ ‐Expanded Graphite Interface for Fast‐Charging Lithium‐Ion Battery Anodes

ABSTRACT Interfacial engineering offers a powerful route to enhance ion transport and electron mobility in lithium‐ion batteries (LIBs) through the induction of built‐in electric fields (BIEFs) at the interface, which in turn facilitates faster Li ⁺ diffusion. Yet, direct experimental validation of this concept in intercalation‐type materials has not been investigated. In this work, bronze titanium oxide (TiO ₂ (B)) is strategically integrated with expanded graphite (EG), producing a strong interfacial BIEF driven by their distinct work functions, as confirmed by Kelvin probe force microscopy (KPFM). As a result, the TiO ₂ (B)/EG electrode delivers a specific capacity of 75 mAh g ⁻¹ at 10 A g ⁻¹ along with 70% capacity retention after 1000 cycles at 2 A g ⁻¹ . Galvanostatic intermittent titration (GITT) and electrochemical impedance spectroscopy (EIS) measurements substantiate the reduction in charge‐transfer resistance accompanied by enhanced Li ⁺ diffusion. Density functional theory (DFT) calculations further verify the presence of the BIEF and clarify its role in lowering Li ⁺ insertion/extraction energy barriers, thereby enabling highly reversible and stable high‐rate operation. Overall, this study demonstrates that BIEF modulation can effectively address the intrinsic kinetic limitations of intercalation‐type materials, offering a viable strategy for the development of next‐generation high‐power, fast‐charging lithium‐ion battery anodes.