Carbon fiber reinforced polyethylene glycol with graft semi-interpenetrating polymer network for battery thermal management and impact resistance

Phase change materials offer energy-saving and uniform temperature control in lithium-ion battery thermal management. Enhancing the mechanical properties of phase change materials enables them to serve as structural protection against impact or accidental damage to batteries. In this work, a composite phase change material with a graft semi-interpenetrating polymer network is developed via a one-step in situ polymerization strategy, in which the polyurethane phase served as the thermal energy storage component and the acrylic copolymer phase provided structural reinforcement. The influence of polyethylene glycol molecular weight on the thermal and mechanical properties of the composite phase change material is investigated, and polyethylene glycol with a molecular weight of 6000 is identified as the optimal matrix component. The resulting g-IPN-PU6000 exhibited a high latent heat of 52.46 J/g and a tensile strength of 13.76 MPa. To further enhance mechanical robustness and interfacial stability, acid-treated short carbon fibers were incorporated into the g-IPN-PU6000 matrix. With 15 wt% acid-treated short carbon fibers, the composite phase change material achieved a tensile strength of 25.04 MPa and an impact strength of 4.31 kJ/m², while maintaining latent heat values in the range of 51.73–70.32 J/g and a phase transition temperature between 52.51 and 57.93 °C. Numerical simulations demonstrated that IPN/ASCF CPCMs could maintain safe battery module temperatures under multiple 1C-2C charge-discharge cycles in various ambient conditions. Experimental results showed that under 3C discharge, the IPN/ASCF CPCM reduced battery temperature rise by 2.2 °C and mitigated battery damage by 45% during drop-ball impact tests. By integrating high latent heat with enhanced mechanical strength, the proposed multifunctional material has great potential to simultaneously perform thermal management and structural protection functions in battery systems.