Heat storage or thermal energy storage is one of the key technologies towards an efficient use of renewable energy resources. Therefore our research group focuses on the development of a heat storage system called “thermal battery” for private households and industry applications. On the one hand especially thermochemical reactions have a high potential for high energy density and long term storage. On the other hand the used materials in particular hygroscopic salts are related to disadvantages such as agglomeration, storage capacity loss over cycling or slow reaction kinetics. Those disadvantages are caused by deliquescence and by the occurrence of side reactions, among other effects. Many studies have been performed in order to overcome and improve those problems [1] for gas-solid reactors. First of all the disturbance caused by deliquescence in salt mixtures of metal chlorides and sulfates appeared to be low in experiments which gives reason to expect better chance of using thermochemical materials. Those mixtures showed improved characteristics in enthalpy of sorption and cycle stability. [2] In the second place the impregnation of carrier substances such as vermiculite or silica gel with aqueous salt solutions reduces the effect of deliquescence and therefore improves the diffusion of water vapor into the material. Two-component composites showed improved cycle stability but lower energy density. [3] We combined the optimization of mixing of salt hydrates and impregnation of carriers. This paper reports on synthesis of thermochemical materials and comparison of the material properites cyclability, energy density and effective thermal conductivity. Last but not least the results will be transferred to the design of a planned heat storage system for household application.