The thermal energy storage material (TESM) system includes a container having a wall surface, and a TESM in at least partial contact with the wall surface. The TESM may include, consist essentially of, or consist of a metal containing compound comprising lithium, one or more different metal cations (i.e., different from lithium) and one or more polyatomic anions. The TESM may have a liquidus temperature, TL, from about 100° C. to about 250° C. The TESM may exhibits a heat storage density from 1 MJ/l to 1.84 MJ/l, as measured from 300° C. to 80° C. The TESM system may be free of water. If any water is present in the TESM system, the water concentration preferably is less than 10 wt. %. Preferably, the TESM system is generally resistant to corrosion at temperatures of about 300° C.