Structural modification and electrochemical performance of graphite–TiO₂ nanocomposite anodes for lithium-ion batteries

Graphite is the most widely used commercial anode material for lithium-ion (Li-ion) batteries owing to its high electrical conductivity, low lithiation potential, low cost, and excellent cycling stability. However, its moderate theoretical capacity and limited density of electrochemically active sites constrain its application in next-generation high-energy-density energy storage systems. In this study, graphite–titania (Gr/TiO₂) nanocomposite anodes with graphite-to-TiO₂ weight ratios of 85:5, 80:10, and 70:20 within the active-material fraction were fabricated to investigate the influence of TiO₂ incorporation on the structural and electrochemical properties of graphite anodes. X-ray diffraction analysis confirmed the coexistence of graphitic carbon and anatase TiO₂ phases without the formation of secondary phases. TiO₂ incorporation progressively increased structural disorder, reducing the graphite crystallite size from approximately 233 nm for pristine graphite to 126 nm for the Gr/TiO₂ (70:20) composite while increasing the lattice microstrain from 6.62 × 10⁻⁴ to 1.22 × 10⁻³. SEM analysis revealed progressive TiO₂ surface decoration and increasing particle agglomeration with increasing TiO₂ content, with the Gr/TiO₂ (80:10) electrode exhibiting an intermediate morphology that preserved the graphite framework while providing substantial TiO₂ coverage. Raman spectroscopy further confirmed the increase in defect density and progressive modification of the oxide–carbon interfacial environment induced by TiO₂ addition. Electrochemical characterization revealed enhanced lithium-storage behaviour following TiO₂ incorporation. Cyclic voltammetry showed that the Gr/TiO₂ (70:20) electrode exhibited the highest voltammetric response, indicating enhanced electrochemical activity and lithium-ion accessibility. Galvanostatic charge–discharge measurements, however, demonstrated that the Gr/TiO₂ (80:10) composite delivered the highest reversible specific capacity of 136.9 mAh g⁻¹, compared with 132.0 mAh g⁻¹ for the Gr/TiO₂ (85:5) composite and 128.1 mAh g⁻¹ for pristine graphite, corresponding to capacity improvements of approximately 6.9% and 3.0%, respectively. In addition, the composite electrodes maintained coulombic efficiencies exceeding 99% during extended cycling, indicating highly reversible lithium insertion/extraction, minimal irreversible lithium consumption, and stable electrode/electrolyte interfacial reactions. The enhanced electrochemical performance is attributed to the synergistic role of TiO₂ as both a structural modifier and an active lithium-storage component, which increases defect density, shortens lithium-ion diffusion pathways, facilitates charge-transfer kinetics, and provides additional lithium-storage sites. These findings demonstrate that controlled TiO₂ incorporation is an effective strategy for improving the structural stability and electrochemical performance of graphite anodes, with the Gr/TiO₂ (80:10) composition providing the most favourable balance between enhanced lithium-storage capacity and electrode conductivity. This highlights the potential of Gr/TiO₂ nanocomposites as promising anode materials for high-performance lithium-ion batteries.