The effects of surface fluorination on the electrochemical charge–discharge properties of a Mg2Ni electrode, prepared by mechanical alloying in Ni-MH batteries are investigated. After 20h milling, Mg and Ni powder form nanocrystalline Mg2Ni. The discharge capacity of this alloy increases greatly on the initial cycle but, due to the formation of a Mg(OH)2 passive layer, displays rapid degradation in alkaline solution within 10 cycles. In a 6M KOH+x M KF electrolyte (x=0.5, 1, and 2), a continuous and stable fluorinated layer is formed and the durability of the Mg2Ni electrode increases marketly and a high rate discharge capability is obtained (90–100mAh/g). Addition of 2M KF leads to the highest durability of all the electrodes tested. The improvement is due to a thin MgF2—flourinated layer, which reduces the charge-transfer resistance and protects the Mg2Ni electrode from forming a Mg(OH)2 layer.