High‐Efficiency Thermal Battery Regulated by Ultralow Magnetic Fields

Controllable thermal storage has emerged as a central theme in advanced energy management, where external stimuli such as light, stress, and pressure can be exploited to precisely regulate heat release. Yet, realizing efficient and practical deployment requires the development of simpler noncontact actuation methods and the enhancement of heat-transfer efficiency, both of which remain major challenges. Herein, a magneto-responsive phase-change composite is presented by integrating a supercooled plastic crystal, 2-amino-2-methyl-1,3-propanediol (AMP), with dispersed NdFeB particles. This design enables noncontact triggering of supercooled phase transitions under ultralow magnetic fields as small as ≈0.04 T. Meanwhile, the dispersed magnetic particles enhance thermal conduction and promote synchronous multipoint crystallization, thereby markedly accelerating heat release. The optimized 20% AMP/NdFeB composite achieves a colossal entropy change of 507.6 J kg^-1 K^-1, a corresponding enthalpy change of 181.1 J g^-1, and a rapid temperature rise of 47.6 K, substantially outperforming leading magnetocaloric systems under far milder field conditions. This work establishes a transformative and generalizable route to noncontact, high-efficiency, and controllable thermal batteries, paving the way for their practical deployment in advanced energy systems.