Using tetramethylammonium hydroxide electrolyte to inhibit corrosion of Mg-based amorphous alloy anodes: A route for promotion energy density of Ni-MH battery

Mg-based alloy anodes suffer from severe corrosion in conventional electrolytes (KOH solution) and this substantially obstructs the cycle life, which is a great challenge for using them in the Ni-MH battery. Herein, a high concentration tetramethylammonium hydroxide (TMAH) aqueous electrolyte with a special hydrate structure is explored and enables excellent cycle stability and high capacity for Mg-based alloy anodes. In this electrolyte, the Mg 0.4 Ti 0.1 Ni 0.5 alloy anode delivers a maximum discharge capacity of 466 mAh g −1 , and maintains 210 mAh g −1 after 100 cycles owing to the reduced corrosion rate , which are much better than that in 6 M KOH electrolyte, being 425 mAh g −1 and 69 mAh g −1 , respectively. Furthermore, by in-situ forming Cu coating on the Mg 0.4 Ti 0.1 Ni 0.5 electrode surface during charging process with the adding 0.01 M of Cu(OH) 2 in TMAH electrolyte, the corrosion of the electrode is further suppressed and the reversible capacity can reach 313 mAh g −1 after 100 cycles. The high conducting Cu coating can also increase the rate capability of the electrode by promoting the charge transfer. Thus, using TMAH electrolytes provides a new approach to promote the electrochemical performances of Ni-MH batteries with Mg-based alloy anodes.