Effect of cobalt doping on the structure and sodium ion intercalation behaviour of birnessite Mn02

Abstract

MnO₂ has many applications for electrochemical power sources such as battery and super-capacitor. In this work, cobalt-doped birnessite MnO₂ was synthesized by the solid route. XRD patterns of cobalt-doped birnessite exhibited the large distance of interlayers at 7.21 Â that is a good possibility for sodium ion intercalation. The electrochemical behaviors of birnessite MnO₂ in NaClO₄/Propylene Carbonate were evaluated by the cyclic voltammetry (CV), charge-discharge cycling. The CV curves proved the reversible insertion of Na⁺ ions in the potential range 1.5-3.8 V (vs. Na⁺/Na). The 10% cobalt-doped birnessite exhibited the highest specific capacity of 150 mAh/g and the fading capacity after 25 cycles due to the modification of structure.