<p>Nanocrystalline green nickel oxide (NiO G) was synthesized via an eco-friendly synthesis route utilizing <i>Citrus limon</i> leaf extract, followed by fabrication of nanocomposites with graphene oxide (GO) through the sonication method for investigating its potential as an anode material in lithium-ion batteries (LIBs). The synthesized nanosized samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) for structural analysis, field emission scanning electron microscopy (FESEM), and scanning electron microscopy (SEM) along with energy dispersive X-ray (EDX) spectroscopy for morphological properties, and UV-Vis spectroscopy and photoluminescence (PL) spectroscopy for optical study. XRD confirmed the pure cubic formation of the NiO G phase, and the average crystallite sizes decreased in the order of 20 nm to 15 nm and 26 to 21 nm, as calculated by the Debye-Scherrer formula and W-H plots, respectively. The FESEM micrograph revealed the reduction of NiO particles from 4.13 µm to 3.20 µm upon GO integration, as calculated by ImageJ software, and EDX spectra confirmed the elemental purity. XPS analysis confirmed the presence of oxygen vacancies and mixed oxidation states (Ni³⁺/Ni²⁺) in the NCG 20 composite. The CV curves showed the distinct reduction and oxidation peaks, followed by better cyclic stability and coulombic efficiency of the NCG-20 electrode, as demonstrated by the GCD curve. The Nyquist plot showed that NCG 20 has the lowest diameter among all negative electrodes, suggesting improved electrochemical performance, low charge transfer resistance, and enhanced Li⁺ diffusion. The study highlights the potential of <i>Citrus limon</i> leaf extract, scalable formation of pure NiO nanoparticles, and incorporation of GO, providing the conductive and large surface area matrix, synergistically enhancing the electrochemical behavior, and offering a sustainable and efficient approach to LIBs anode material.</p> Graphical Abstract <p></p>