Effective thermal management is critical to the performance, lifespan, and safety of lithium-ion batteries in electric vehicles (EV). Transient and non-uniform temperature distributions within cells accelerate degradation, cause pack imbalance, and reduce efficiency. Localized hotspots, in particular, promote lithium plating, solid electrolyte interface (SEI) growth, and other failure mechanisms. Persistent non-uniformities increase the likelihood of thermal runaway under high-stress operation. To address these challenges, this work develops a one-dimensional thermal model that captures heat generation and dissipation under dynamic operating conditions, incorporating both conduction within the cell and active convective cooling. Using a DFSS-based approach, we evaluate design and cooling strategies that minimize temperature differentials while maintaining acceptable operating ranges. The findings provide practical guidance for battery thermal management system design, emphasizing