Enhanced Cycling Stability of Amorphous MgNi-Based Alloy Electrodes through Corrosion Prevention by Incorporating Al₂(SO₄)₃·18H₂O into the Electrolyte

Abstract

Mg-based alloy anodes suffer from severe corrosion in alkaline electrolytes, which substantially impedes their cycle life and thereby limits their suitability as anode materials for nickel–metal hydride (Ni-MH) batteries. This work modifies the conventional 6 M KOH electrolyte by adding 0.1 M Al2(SO4)3·18H2O. The electrochemical hydrogen storage properties of Mg0.45Ti0.05Ni0.50 alloy in this electrolyte and its microstructural evolution during cycling are studied. In the 6 M KOH + 0.1 M Al2(SO4)3·18H2O electrolyte, a protective layer consisting of Mg2Al(OH)7 is formed on the surface of the Mg0.45Ti0.05Ni0.50 alloy anode during charge/discharge cycling instead of Mg(OH)2, effectively preventing further corrosion and improving its cycle life. The Mg0.45Ti0.05Ni0.50 alloy anode delivers a maximum discharge capacity of 479.0 mAh g−1 and maintains 318.4 mAh g−1 after 30 cycles in the 6 M KOH + 0.1 M Al2(SO4)3·18H2O electrolyte, which is significantly superior to that achieved in the 6 M KOH electrolyte (471.1 mAh g−1 and 201.8 mAh g−1, respectively). This work provides a new strategy for improving the cycle stability of Mg-based alloy anodes.

Keywords

• Ni-MH battery
• Mg-based alloys
• corrosion
• cycle life