Comparison of the Effect of Coaddition of Li Compounds and Addition of a Single Li Compound on Reactivity and Structure of Magnesium Hydroxide

Abstract

Mg(OH)2 is a chemical heat storage material that is studied for the utilization of 300–350 °C waste heat. In this study, LiCl and LiOH were coadded to Mg(OH)2, and the reactivity and structural evolution were investigated. In the hydration of samples at 200 °C subsequent to dehydration at 270 °C, Mg(OH)2 with coadded LiCl and LiOH showed excellent hydration reactivity, with a heat output density of 1053 kJ kg–1. The coaddition of LiCl and LiOH enhanced both the dehydration and the hydration reactivity of Mg(OH)2. X-ray diffraction analysis indicated that the addition of LiOH to Mg(OH)2 promoted the decomposition of Mg(OH)2 and the diffusion of water on the surface of Mg(OH)2, whereas the addition of LiCl to Mg(OH)2 promoted these processes in the bulk phase of Mg(OH)2.

Fourier-transform infrared and X-ray diffraction analyses of the hydration reaction of pure magnesium oxide and chemically modified magnesium oxide

“…Salt hydrates such as MgCl 2 $6H 2 O, 14,15 LiOH$H 2 O, 16 and metal sulfates 15,[17][18][19] have been used as CHS materials in the temperature range of 100-250 C. Mg(OH) 2 , [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Ca(OH) 2 , 28,[35][36][37] and MgCO 3 (ref. 38) can be used to store energy in the temperature range of 200-500 C. These materials exhibit high energy density and the property of reversibility.…”

“…The dehydration reaction of Mg(OH) 2 and the hydration reaction of MgO correspond to the heat storage and output operations, respectively. The rate of dehydration of Mg(OH) 2 is signicantly slow when the temperature is <300 C. A signicantly low hydration reactivity is observed for MgO in the temperature range of 150-200 C. 24,31,33 Therefore, the difference in the dehydration and hydration temperatures is one of the problems for the widespread application of CHS materials because the difference leads to the waste of sensible heat. 18 We proposed that the addition of LiCl and/or LiOH to Mg(OH) 2 samples can help improve the dehydration reactivity.…”

“…18 We proposed that the addition of LiCl and/or LiOH to Mg(OH) 2 samples can help improve the dehydration reactivity. [22][23][24]32,33 The rate of dehydration of Mg(OH) 2 in the temperature range of 270-300 C increased signicantly when Li compounds were added. [22][23][24]32,33 The hydration reactivity of the MgO system where both LiCl and LiOH were used as additives (at 200 C) was signicantly higher than the hydration reactivity of the MgO system containing either LiCl or LiOH.…”

“…[22][23][24]32,33 The rate of dehydration of Mg(OH) 2 in the temperature range of 270-300 C increased signicantly when Li compounds were added. [22][23][24]32,33 The hydration reactivity of the MgO system where both LiCl and LiOH were used as additives (at 200 C) was signicantly higher than the hydration reactivity of the MgO system containing either LiCl or LiOH. 33 We have identied the roles played by LiCl and LiOH during the dehydration of Mg(OH) 2 .…”

Tuning Mg(OH)2 Structural, Physical, and Morphological Characteristics for Its Optimal Behavior in a Thermochemical Heat-Storage Application

“…These promising properties encouraged many researchers to study the optimization of the Mg(OH) 2 /MgO system for TES applications. Kurosawa et al added LiCl and LiOH to Mg(OH) 2 , reaching a heat output density of 1053 kJ/kg [ 25 ]. Furthermore, Ishitobi et al rose a heat output density per unit weight of LiCl-modified Mg(OH) 2 of 1400 kJ/kg [ 26 ].…”