Lithium-ion batteries suffer from severe capacity fading and start-up failure at low temperatures owing to restricted Li⁺ transport and deteriorated interfacial kinetics. To enable rapid and safe activation under such conditions, this study designs a microwave-driven dual-layer leakage-proof composite phase-change module (EPG–BN–CF–PAG), comprising an epoxy–graphene–boron nitride outer encapsulation and a ceramic fiber–boron nitride porous inner scaffold that adsorbs a paraffin–graphene phase-change core. The synergy between the dense outer shell and the internal adsorption framework affords excellent shape stability, with an enthalpy retention exceeding 95% and no visible leakage after 20 heating–cooling cycles. Owing to the strong microwave-absorption capability of graphene, the module can be rapidly heated from −10 °C to ~60 °C within 60 s while establishing a homogeneous and stable temperature field. Combined simulations and experiments show that the module efficiently transfers heat to a lithium-ion cell, raising its temperature from −10 °C to ~30 °C within 60 s and thus bringing it into a practical operating window. Electrochemical impedance spectroscopy further reveals that the thermally induced activation markedly improves interfacial kinetics, reducing the bulk resistance from 500 Ω to 30 Ω and the charge-transfer resistance from 800 Ω to 30 Ω. This microwave-driven phase-change heating strategy features ultrafast response, excellent anti-leakage performance, and favorable thermal properties, providing an engineering-feasible thermal-management solution for the rapid cold start of lithium-ion batteries under extremely low-temperature conditions.