This study investigates the complex interaction between Rayleigh–Bénard and Marangoni convection in liquid metal batteries (LMBs), which are essential for efficient large-scale energy storage. The challenge addressed is understanding how temperature gradients and layer thickness influence heat transfer and stability within LMBs, as effective thermal management is critical for improving battery performance and longevity. Using computational simulations, we modeled the fluid dynamics within a three-layer LMB system, observing how temperature-driven convection patterns, driven by buoyancy (Rayleigh–Bénard) and surface tension (Marangoni) forces, affect heat transfer. Key findings include that thinner middle layers enhance Marangoni effects, leading to a more efficient convective heat transfer, while thicker layers reduce this effect, impacting overall battery efficiency. This study also identifies critical conditions where these convection modes interact or destabilize, impacting the battery's thermal performance. This study introduces a novel approach by quantitatively demonstrating the joint influence of layer thickness and temperature gradients on heat transfer efficiency in liquid metal batteries, optimizing thermal management strategies beyond previous models.