The rapid expansion of micromobility necessitates safe, compact, and efficient energy storage. Li-ion cells generate substantial heat during high-load operation and fast charging, posing a significant challenge in the confined mounting spaces typical of small electric vehicles. Traditional active cooling systems are often impractical due to cost, weight, and power requirements. This study proposes an innovative, low-cost composite Phase Change Material (PCM) based on soy wax doped with nanographite and High-Density Polyethylene (HDPE) to enhance thermal dissipation. The composite was characterized using Differential Scanning Calorimetry (DSC) to determine specific heat, phase transition temperatures, and heat capacity. Molecular structure was analyzed via Scanning Electron Microscopy (SEM) and Raman spectroscopy. Thermal conductivity and diffusivity were measured using the Hot Disk method (ISO 22007). Results indicate that the nanographite-doped composite significantly outperforms pure organic materials (paraffin, soya wax, beeswax) in thermal transport properties. For experimental validation, the PCM was integrated into 3D-printed LFP cell molds using the Melting-Diffusion-Molding (MDM) method. Radiometric data from Flir Research Studio PRO and Matlab were processed using edge segmentation and internal morphological semi-gradient methods to optimize cell spacing and PCM volume. The influence of PCM on the State of Energy (SoE) was identified through Hybrid Pulse Power Characterization (HPPC). Cell dynamics were modeled using 1st, 2nd, and 3rd-order Thevenin equivalent circuits. Parameter identification was performed via Levenberg-Marquardt and Particle Swarm Optimization (PSO) algorithms. Model accuracy was verified using Root Mean Square Error (RMSE) and coefficient of determination (R2) across the full State of Charge (SoC) range. Testing on single cells and 6s1p modules (SimScape/QuickerSim) demonstrates that this methodology is scalable and applicable to Li-ion, Na-ion, and solid-state technologies, providing a robust solution for mobile, self-sufficient energy storage systems.