Ultrahigh-performance solid-solid phase change material for efficient, high-temperature thermal energy storage

Thermal energy storage using phase change materials (PCMs) offers enormous potential for regulation of unmatched energy supply and demand of renewable energy resources, recycling of waste thermal energy, and thermal management in high-power electronic devices. However, solid-liquid PCMs, which are the most commonly used PCMs, suffer from fatal drawbacks of liquid leakage, shape instability and severe corrosiveness at elevated temperatures, posing a great threat to the stability, safety and service life of thermal energy storage systems. Here, we developed a class of novel, ultrahigh-performance solid-solid PCMs. A giant figure of merit of 9056 × 106 J2/(K⋅s⋅m4), much higher than most existing PCMs (for instance, 15 times higher than commercial PCMs), was achieved by employing the large latent heat, high thermal conductivity and high density of these metallic Ni-Mn-Ti PCMs. Furthermore, these materials have tunable high phase-transition temperatures (290–500 °C), suitable for applications at different elevated temperatures, and exhibit superior thermal cycling stability. Being solid-solid PCMs, they possess inimitable advantages of no leakage risk, no corrosiveness and shape stability. Therefore, these Ni-Mn-Ti solid-solid PCMs are a robust candidate for efficient, compact and endurable high-temperature thermal energy storage applications. Our in-situ neutron diffraction experiment reveals a large unit cell volume change (2.49%) across phase transition and good geometric compatibility between the transforming phases, accounting for the large latent heat and superior thermal cyclability, respectively. This work opens a new avenue for designing advanced high-performance solid-state thermal energy storage materials.