In the era of sustainable energy transition, energy storage technology has become a crucial factor in supporting electric vehicles, electronic devices, and renewable energy storage systems. One of the most widely used technologies today is the lithium-ion battery, owing to its high energy density and reliable electrochemical performance. However, significant challenges remain, particularly regarding the availability of high-quality raw materials at competitive costs. This research focuses on investigating the effect of sintering temperature on the structure of LiNi0.8Mn0.1Co0.1 (NMC 811) cathode materials synthesized from locally sourced precursors. This material is chosen due to its high energy capacity combined with good electrochemical stability. By applying sintering at various temperatures, this study examines how processing conditions influence the crystal structure, morphology, and chemical composition of the cathode material. Several material characterization techniques are employed to support the investigation, including FTIR (Fourier Transform Infrared Spectroscopy) to identify functional groups, XRD (X-ray Diffraction) to analyze crystal structures, SEM (Scanning Electron Microscopy) to observe particle morphology, and XRF (X-ray Fluorescence) to determine elemental composition. The research results are expected to provide meaningful contributions to the development of the national battery industry. By utilizing domestic mineral resources such as nickel and manganese, Indonesia has the potential to reduce dependency on imported raw materials while increasing the added value of local resources. Furthermore, this study forms part of a long-term research roadmap aimed at developing battery prototypes and advancing toward downstream technology implementation. This effort aligns with the mission to accelerate clean energy adoption in Indonesia and to support the transformation toward a self-reliant green technology era.