The increasingly prominent energy and environmental problems are pushing the requirements of our society for improved energy conservation and environmental protection. The requirements for efficient energy use are also increasingly higher. Thermal energy storage (TES) technologies are valuable components in many energy systems and could be an important tool in achieving a low-carbon future.

Phase-change materials (PCMs) are a thermal energy storage technology categorised by their capacity to store latent heat and are particularly attractive for applications where thermal energy has to be stored or delivered over a narrow temperature range or when compactness is a requirement.

Most widely used PCMs undergo solid-liquid transitions (solid-liquid PCM) and at the phase transition temperature, their temperature remains constant since the external heat is no longer used to change the temperature of the material but to change its state. As a consequence, the energy involved in the phase transition of the PCM, i.e., the specific enthalpy difference between solid and liquid (at constant temperature) also known as latent heat, is absorbed or released on the melting-solidification process of the PCM.

Solid-liquid PCMs require encapsulation in order to prevent the leakage of the liquid phase, and porous materials like clay minerals, metal foams or porous carbon are used to manufacture composite PCMs. However, the different containment strategies have limitations in terms of encapsulation efficiency and/or low enthalpy values.