## 5 Conclusions  
Here, we investigated a composite material based on silicone vapor-permeable foam filled with 40 wt.% of LiCl (LiCl-PDMS), aiming at confining the salt in a matrix to prevent deliquescence-related issues but without inhibiting the vapour flow. Specifically, we studied the structural and morphological modification of the composite foam during  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Li Composite**} & **LiCl Content** & **Stored/Released Heat** & **Energy Storage** & **Charging/Discharging Conditions** & & \\  & **(wt.\%)** & **(kJ/kg\({}_{\text{composite}}\))** & **Density (kWh/m\({}^{3}\))** & **T\({}_{\text{char}}\)** (\({}^{\circ}\)C)** & **T\({}_{\text{diss}}\)** (\({}^{\circ}\)C)** & **RH\({}_{\text{diss}}\)** (\%)** & **Ref.** \\ \hline \hline
**Li-PDMS foam** & 40 & 1854 & 323 & 80 & 35 & 22 & this work \\
**LiCl/activated alumina** & 14.68 & 874 & 318 & 120 & 20 & 80 & [18] \\
**LiCl/Siegel** & 31.10 & 1000 & 166 & 66 & 35 & 15 & [30] \\
**LiCl/Vermiculite** & 45.20 & 1250 & 111 & 66 & 35 & 15 & [30] \\
**LiCl/MWCNTs** & 41-42 & 1700 & n.a. & 75-46 & 65-35 & 15 & [20] \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of some LiCl-based composites’ energy densities and testing conditions.  
Figure 7: (**a**) TG/DSC profile of LiCl-PDMS foam under the temperature drop of 80–35 \({}^{\circ}\)C at 12 mbar of water vapor pressure, corresponding to 10 \({}^{\circ}\)C of evaporation temperature. (**b**) Deconvolution of DSC profile.  
the hydration/dehydration cycles through in situ XRD and ESEM analysis. In situ XRD enabled the material dehydration reaction from room temperature up to 80 \({}^{\circ}\)C, while the environmental SEM analysis simulated the hydration/dehydration reaction conditions, thus allowing for the evaluation of the interaction between the salt and the water vapor environment in the confined silicon matrix. The results show an effective embedding of the material, which limits the salt solution release when overhydrated. Additionally, the flexibility of the matrix allows for the volume shrinkage/expansion of the salt caused by the cyclic dehydration/hydration reactions without any damages to the foam structure. Indeed, as lithium chloride transformed from monohydrate to anhydrous, a significant volume contraction was observable (~70% of its initial volume). The LiCl-PDMS foam energy density was measured with a customized coupled thermogravimetric/differential scanning calorimetric analysis (TG/DSC) during the hydration phase and the estimated energy density value was ~1854 kJ/kg (or ~323 kWh/m\({}^{3}\)), thus making it a competitive candidate among other LiCl salt hydrate composites.  
Conceptualization, L.C. and E.P.; investigation, E.P., A.F., D.P. and E.M.; data curation, E.M. and D.P.; validation, L.C., E.P., A.F. and E.M.; writing--original draft preparation, E.M.; writing--review and editing, E.M., E.P. and L.C. All authors have read and agreed to the published version of the manuscript.  
This research study was funded by the Italian Ministry of University and Research (MUR), program PON R&I 2014/2020--Avviso n. 1735 del 13 July 2017--PNR 2015/2020, under project \"NAUSICA--NAvi efficienti tramite l'Utilizzo di Soluzioni tecnologiche Innovative e low Carbon\", CUP: B45F21000680005.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.