By reporter Chunlei Shen — Recently, researchers from the Institute of Metal Research, Chinese Academy of Sciences (IMR, CAS), the Beijing High Pressure Science Research Center, and Shanghai Jiao Tong University have jointly discovered the first inverse barocaloric (BC) material system — ammonium thiocyanate (NH₄SCN). This discovery successfully extends the application of barocaloric materials into the field of thermal energy storage. The related findings were published in Science Advances.
Since the discovery of the colossal barocaloric effect in 2019, researchers from the Functional Materials and Devices Division at the Shenyang National Laboratory for Materials Science, IMR, have been actively engaged in the systematic investigations in this field. Their efforts have led to the identification of several high-performance materials, including ammonium iodide, carborane, and potassium hexafluorophosphate, along with conceptual designs for solid-state cooling prototypes. These advances have opened a new technological route toward the development of zero-carbon refrigeration technologies.
According to Prof. Bing Li, one of the corresponding authors and a researcher at IMR, in contrast to the normal barocaloric effect (where heat is released upon compression and absorbed upon decompression), the inverse barocaloric effect exhibits the opposite behavior — heat absorption during compression and heat release during decompression — a phenomenon that is extremely rare. “Utilizing inverse barocaloric materials enables not only solid-state cooling but also the construction of pressure-controlled thermal energy storage technologies,” said Li.
Currently, global energy utilization faces a “thermal paradox”: heat production accounts for over 50% of total final energy consumption and contributes to about 30% of global carbon emissions. Meanwhile, approximately 72% of primary energy is dissipated as heat during energy conversion. Li pointed out that if the lost thermal energy can be collected, stored, and reused in the form of heat, it would significantly enhance energy efficiency and reduce carbon emissions. However, temperature-based thermal control inherently suffers from energy dissipation and poor tunability. Therefore, non-thermal external fields, such as pressure, have become an important means for regulating heat energy and have attracted growing attention in the scientific community.
In this study, the researchers achieved pressure-controlled thermal energy management using the inverse barocaloric effect of NH₄SCN, which involves three main steps:
1.The material comes into contact with a heat source and absorbs heat upon compression, thereby cooling the source.
2.Under constant pressure, the absorbed heat can be stored stably for long periods without dissipation due to environmental temperature fluctuations.
3.Upon decompression, the material releases heat, enabling efficient recovery and reuse of residual heat.
“Through in-situ neutron diffraction, synchrotron X-ray diffraction, and inelastic neutron scattering, combined with first-principles calculations and molecular dynamics simulations, we found that the suppression of hydrogen-bond interactions under pressure is the origin of the inverse barocaloric effect,” said Li. “This pressure-induced atomic disorder is highly unusual — completely opposite to the high-pressure behavior observed in most materials.”
For more information: https://doi.org/10.1126/sciadv.add0374
The above is a translated version of the related report published by China Science Daily on February 20, 2023.
