Electrochemical insertion of magnesium in a mixed manganese–cobalt oxide

Abstract

The electrochemical insertion of Mg ²⁺ into the cation-deficient mixed oxide Mn _2.15 Co _0.37 O ₄ is studied in regard to its possible use as a positive electrode in magnesium ion-transfer batteries. The cation vacancies of the mixed oxide offer a pathway for Mg ²⁺ insertion with a maximum uptake of 0.23 Mg per mole of oxide. Voltammetric and chronopotentiometric measurements indicate a single insertion step located near 2.9 V vs Li/Li ⁺ . The strong polarizing effect of Mg ²⁺ ions induces a more pronounced disordering process than for Li accommodation. This results in a limited stable specific capacity of 30 A h kg ^-1 when discharge–charge cycles are performed at a C/6 rate within the cycling limits 4.05–1.85 V vs. Li/Li ⁺ .