High-entropy Ti-Zr-Hf-Ni-Cu alloys as solid-solid phase change materials for high-temperature thermal energy storage

High-performance high-temperature solid-solid phase change materials (SS-PCMs) are urgently demanded for thermal energy storage and thermal management at elevated temperatures in the rapidly developing energy and information industries. Here, we report a novel class of Ti-Zr-Hf-Ni-Cu high-entropy alloys showing high thermal-energy-storage performance at elevated temperatures, which are a robust candidate for high-temperature SS-PCMs. Notably, the figure-of-merit values of these Ti-Zr-Hf-Ni-Cu SS-PCMs are an order of magnitude higher than that of traditional SS-PCMs, due to their much higher thermal conductivity and satisfactory volumetric energy storage capacity as compared to traditional SS-PCMs. Furthermore, the phase transition temperatures of these SS-PCMs can be easily and precisely tuned by composition change, in a wide high-temperature range of 300-470 degrees C. These high figure-of-merit SS-PCMs with high thermal conductivity have extremely promising prospects for advanced thermal energy storage and compact high-power-density electronic cooling applications. This work opens a new field for exploring high-entropy alloys as solid-solid thermal-energy-storage phase change materials.