Redox properties of alluaudite sodium cobalt manganese sulfates as high-voltage electrodes for rechargeable batteries.

Alluaudite sulfates are predicted to be high-voltage electrodes for lithium- and sodium-ion batteries. Herein, we provide the first experimental evidence for the operation of sodium cobalt-manganese sulfate, Na2+2δ(Co0.63Mn0.37)2-δ(SO4)3, at potentials higher than 4.0 V vs. Li/Li+. This fact comes as a result of the reduced cationic deficiency, redox properties of Co and Mn and stability of the alluaudite structure during alkali ion intercalation.