Abstract: Thermoelectric cementitious composites using temperature difference power generation can realize the mutual conversion of thermal and electrical energy to reduce urban environmental temperature and resource consumption, but the low efficiency of thermoelectric conversion and vulnerability to environmental impact have restricted its large-scale application. To address this issue, this study proposes the addition of highly conductive expanded graphite (EG) to boron-doped carbon nanotubes (B-CNTs) with high Seebeck coefficients to improve the overall power factor of cementitious composites by the synergistic effect of multi-scale hybridization of B-CNTs and EG. The power factor of the cementitious composites was improved by 10 times to 1.49 μW·m⁻¹·℃⁻² compared with that of the cementitious composites without the addition of expanded graphite. The EG-B-CNTs/cement composites after freeze-thaw cycling result in increased porosity and the presence of moisture, which introduce high-density defect interfaces such as solid-solid and liquid-solid, resulting in an increase in carrier scattering intensity and an enhanced Seebeck coefficient for freeze-thaw cycling of cement matrix composites. The power factor of 10.0wt%EG-5.0wt%B-CNTs/cement composite is 1.54 μW·m⁻¹·℃⁻² when freeze-thaw cycles are performed 15 times. The research in this paper provides a theoretical basis for improving the performance and environmental conditions of thermoelectric cement matrix composites for future viable applications.