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

Abstract

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, Na_2+2δ(Co_0.63Mn_0.37)_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.