This paper presents the results of investigation of energy-efficient materials for Ni-MH batteries based on Ni substitution by Mn in the NdY2Ni9 alloys. Synthesized using arc melting and annealing, the alloys crystallize in a LaY2Ni9 type of structure. Electrochemical studies reveal nonlinear effects of Mn substitution on discharge capacity. The highest discharge capacity was found for the NdY2Ni8Mn alloy with 352 mAh/g, retaining 73% capacity after 50 charge/discharge cycles.