Hybrid thermal management of lithium-ion batteries using ternary nanoparticle-enhanced water and PCM embedded in graded porous media

• A novel hybrid battery cooling system combines PCM, water, ternary nanofluids, and graded porous media to enhance heat dissipation. • Enhancing thermal conductivity with ternary nanoparticles effectively reduces battery temperature during high-rate discharges. • The proposed system lowers peak battery temperature by 44.47 K at a 5C discharge, enhancing safety and thermal performance. • The optimized design, using graded porous media, achieves excellent temperature uniformity with a maximum cell-to-cell difference of only 0.54 K. This study presents a comprehensive numerical investigation of an advanced hybrid battery thermal management system (BTMS) for lithium-ion batteries. The proposed system integrates passive phase change material (PCM) cooling and active water-based convection, further enhanced by dual ternary nanofluids and porous media. Five configurations are evaluated: (i) passive cooling using pure PCM, (ii) hybrid cooling with PCM and water, (iii) nano-enhanced hybrid using MgO-ZnO-MWCNT in the PCM and Al₂O₃-Cu-Graphene in the coolant, (iv) nano-enhanced hybrid with uniform porous media (ε = 0.85–0.98), and (v) nano-enhanced hybrid with spatially graded porous structures (ε = 0.98 → 0.85 in the x- or y-direction). Simulations are conducted under discharge rates of 1C, 3C, and 5C, with Reynolds numbers ranging from 50 to 300. Results show that the nano-enhanced hybrid reduces the maximum temperature by up to 0.95 K compared to the standard hybrid case, and by more than 10 K compared to the pure PCM configuration. At a 3C discharge rate, increasing the Reynolds number to 300 further reduces the peak temperature by 1.61 K. Uniform porous media improve temperature uniformity, while the graded porous structure offers the best overall thermal performance. At 5C discharge, the optimized system—with nano-enhanced PCM and coolant embedded in graded porous media (ε = 0.98 → 0.85, x-direction)—achieves a maximum cell temperature of 311.75 K and a temperature difference of just 0.54 K, significantly outperforming the passive PCM case (356.22 K and 2.09 K, respectively; ΔT = 44.47 K). The findings demonstrate the high potential of combined nanofluid and porous media strategies for effective and uniform thermal regulation in high-performance EV battery systems.