Fabricating advanced metal oxide pellets for superior heat storage stability

Heat storage is becoming increasingly important from the perspective of energy storage. Among the various thermochemical heat storage materials, MgO has garnered interest as a heat storage material at moderate temperatures (200–400 °C) owing to its low price, non-toxicity, and high heat storage density. However, the practical integration of MgO into a thermal energy storage system is challenging because of its low cycling stability, which is largely attributed to the agglomeration of its powder. Although pelletization has been proposed as a solution to cycling instability, structural instability due to volume changes during heat storage cycles remains a concern. In this study, an MgO-based heat storage pellet was successfully developed using a fabrication strategy that involved the direct molding of char, the introduction of a sintering process, and the incorporation of ceramic fibers. Consequently, superior heat storage performance and cycling stability observed in the developed MgO-based heat storage pellet can be attributed to various factors. The hierarchical pore structure and small particle size facilitate efficient material transport and provide a large surface area, leading to superior heat storage performance. Additionally, the necking and toughening effects due to sintering help overcome structural instability during heat storage cycles, resulting in robust structural stability. It is expected that the developed pelletization technology, which allows to overcome the inherent cyclic instability, will contribute significantly to the practical implementation of MgO as a heat storage material.