Abstract: A novel synthesis of the large tunnel structure Mg-containing Todorokite from nano6-MnO₂ and 3mol/L MgCl₂ in a higher pressure caldron was described. XRD and TEM results confirm that Mg-Todorokite is also a nano-phase MnO₂ with homogeneous particle size. Electrochemical studies on constant current discharge and cyclic behavior of Mg-Todorokite in 9mol/L KOH or in 5mol/L LiNO₃ aqueous electrolytes show that it possesses a lower open circuit voltage, and a good cycling performance.

Key words: Mg-Todorokite, large tunnel structure, constant current discharge, cyclic voltammetry