Thermal effects impact battery performance, safety, and health. Existing models of heat generation, conduction, and dissipation in batteries account for distinct physicochemical properties of the active material and electrolyte but routinely disregard the presence of the carbon binder domain (CBD), which ensures the electrodes' cohesiveness and structural stability. We present a homogenized thermal model for a spherical active particle coated with CBD and immersed in a liquid electrolyte. The model replaces this composite particle with a homogeneous particle whose equivalent thermal conductivity and other properties preserve the amount of released heat and heat flux at the solid/electrolyte interface, for a given ambient temperature. The effective thermal conductivity is expressed in terms of the volume fraction of the active material in the mixture and the electrochemical and thermal properties of both the active material and CBD. This analytical expression for thermal conductivity can be readily integrated into thermal simulations at either device-scale or pore-scale, without adding computational complexity. Consequently, it provides a means to account for CBD in models used for battery design and management.