Fabrication of TiFe-Based Electrodes Using High-Energy Ball Mill with Mn Additive for NiMH Batteries

Binary and ternary (with the addition of Mn) TiFe-based intermetallic compound powders were fabricated by high energy ball milling, and their electrochemical behavior as negative electrodes was investigated in 6M-KOH. X-ray diffraction exhibited the single phase of nanostructured binary and ternary TiFe-based crystallites after 20 h of milling followed the amorphous phase formation. Addition of Mn increased peak broadening and in turn decreased the nanocrystallite size of TiFe. Electrode properties of 20, 40, 60, and 70 h binary milled products showed that the discharge capacity of the 60 h one offered a maximum discharge capacity of ~169 mAhg⁻¹. Although substitution of Mn for Ti (Ti_1−xFeMn_x, x = 0.1, 0.2) caused a decrease in initial discharge capacity, the periodic stability increased compared to the binary TiFe and ternary TiFe_1-xMn_x (x = 0.1, 0.2). The ternary Ti_0.9FeMn_0.1 electrode maintained ~53% of its initial discharge capacity after five cycles of charge–discharge; this was just 28% in the case of binary TiFe electrode.