Thermochemical heat storage (TCHS) systems offer promising solutions to the global energy problem by storing energy produced by renewable sources in a very veritable manner. In this context, the structural and thermal energy storage performance of Ammonium Tutton salts NH4T-M (M = Zn, Mg, Cu, Ni, Fe) were investigated as thermochemical heat storage materials (TCM). The thermal measurements of these materials revealed suitable operating conditions with a good storage density for low to mid-temperature applications. The compatibility test provided severe corrosion behavior of Cu/NH4T-Cu and Cu/NH4T-Fe due to the strong pitting corrosion damages confirmed by SEM microscopy and the corrosion products were revealed by XRD and Raman spectroscopy. The obtained results showed that NH4T-Zn was qualified as the prospective candidate for TCHS with the highest storage density of 1214.6 kJ/kg and less corrosive behavior. Meanwhile, the cycling stability showed a significant storage density decrease of 24.2% after 20 cycles. A novel composite TCM was developed based on NH4T-Zn impregnated into expanded graphite (EG). NH4T-Zn@EG provided a high storage density of 1080.6 kJ/kg inducing an enhancement of 68.7% compared to the unimpregnated salt with high cycling stability. Also, the corrosion resistance of Cu/NH4T-Zn@EG involved an improvement of 39.6% opening the route towards new researches concerning the development of the NH4T-Zn@EG system. (c) 2020 Elsevier Ltd. All rights reserved.