Synergistic CuO/MgO nucleation for low-supercooling Na2SO4·10H2O in battery thermal management

Abstract

Sodium sulfate decahydrate (Na₂SO₄·10H₂O, SSD) is a promising low-temperature phase change material (PCM) but suffers from severe supercooling upon melting. To address this limitation, we developed SSD-based composites incorporating nanostructured flower-like CuO (f-CuO) and porous MgO (p-MgO) as heterogeneous nucleation agents. f-CuO offers high dispersibility, while p-MgO, with a specific surface area approximately 13 times greater than that of f-CuO, exhibits superior spatial overlap with dehydrated SSD clusters. Cooling curve analysis showed that f-CuO and p-MgO individually reduced the supercooling to 5.4 °C and 2.7 °C, respectively. Notably, a hybrid 1 : 4 mixture (f-CuO : p-MgO) achieved the lowest supercooling of 1.8 °C. Despite the addition of nucleation agents, the composite maintained a latent heat of 184.8 J g⁻¹, retaining 83% of pure SSD. Furthermore, when this hybrid SSD composite was coated onto an Al alloy substrate, it delayed the temperature rise by 3.9 °C and prolonged the time to reach the target temperature of 50 °C by approximately 5 minutes under continuous heating, thereby demonstrating excellent thermal buffering performance. These results highlight the effectiveness of a dual-agent nucleation strategy in minimizing supercooling without compromising heat storage capacity, offering significant potential for passive thermal regulation in lithium-ion battery systems operating in the 30–50 °C range.