Enhancement of hydration rate of LiOH by combining with mesoporous carbon for Low-temperature chemical heat storage

Abstract

The reversible reaction between lithium hydroxide (LiOH) and lithium hydroxide monohydrate (LiOH·H2O) is promising for low-temperature chemical heat storage below 373 K, because this system can store heat at ∼340 K with a high storage density of 1440 kJ/kg. However, for practical applications, it is necessary to enhance the hydration rate of LiOH and thus achieve a higher heat release rate. In this study, we focused on a composite of LiOH and mesoporous carbon (MPC). LiOH was expected to rapidly react with the moisture condensed in the pores of MPC by capillary condensation. The LiOH/MPC composite was prepared by an impregnation method using aqueous LiOH solution concentrations of 1–10 wt% and at impregnation times of 1–48 h. It was demonstrated that LiOH was successfully supported on MPC and that the LiOH content linearly increased with increasing aqueous LiOH solution concentrations. All LiOH/MPC composites had a much higher amount of hydrated water throughout the hydration period than did LiOH or MPC, individually. Comparison of the experimental and estimated values of the amount of hydrated water and endothermic heat after 10 min of hydration showed that most of the LiOH was hydrated within 10 min in the case of the LiOH/MPC composite. From these results, it was demonstrated that LiOH supported on MPC was very effective in improving the hydration rate of LiOH.