Sodium energy storage devices employing aspects of both ZEBRA batteries and traditional Na—S batteries can perform better than either battery alone. The hybrid energy storage devices described herein can include a sodium anode, a molten sodium salt catholyte, and a positive electrode that has active species containing sulfur. Additional active species can include a transition metal source and NaCl. As a product of the energy discharge process, Na2Sx forms in which x is less than three.