Large thermal hysteresis enabled caloric batteries

Minimizing the utilization of fossil fuels and mitigating CO2 emissions are two of the most significant worldwide concerns in the current century. The pervasive waste heat not only results in great energy wastage but also poses a great environmental concern. Typical phase change materials (PCMs) suffer from uncontrolled thermal energy utilization as a result of spontaneous heat loss. We provide a new approach to thermal energy storage that challenges the traditional notion of minimizing hysteresis in solid-state refrigeration using PCMs. Instead, we introduce a second stimulus, such as uniaxial stress, magnetic field, electric field, or hydrostatic pressure, to take advantage of the hysteresis phenomenon. This enables us to prevent spontaneous heat loss by implementing a hysteresis energy barrier when the PCMs come into contact with cooler surroundings. Additionally, we may actively regulate the release of thermal energy using a secondary stimulus. The technological viability of these thermal batteries is proven through the utilization of TiNiNb, MnNiCoGeSi, BaTiO3, and neopentylglycol, respectively. Notably, by machine-learning-guided design, Ni50Ti40Zr8.75Nb1.25 alloy was prepared and shown to be an outstanding choice for thermal batteries due to its appropriate and exceptionally broad working temperature range (71 K). Our study offers a new strategy for developing thermal energy storage materials and it is anticipated to greatly enhance the utilization of waste heat.