Progress of hydrogen storage alloys for Ni-MH rechargeable power batteries in electric vehicles: A review

As clean energy materials, hydrogen storage alloys have been widely investigated and applied as negative electrodes for nickel-metal hydride (Ni-MH) rechargeable batteries due to their high energy densities and environment-friendliness. This review details the progress made in the last few decades on hydrogen storage alloys, such as AB5-type alloys, AB2-type alloys, Mg-based alloys, Ti-V-based alloys and RE-Mg-Ni (rare earth abbreviated as RE) alloys, for Ni-MH rechargeable batteries. The principles of Ni-MH batteries and the relationship between electrochemical performance and hydrogen storage properties have been narrated in detail. The achieved research results, existing problems and development direction are discussed systematically. The relationship between alloying compositions, crystal structures and electrochemical properties for each alloy type are also noted and analyzed with the emphasis on power batteries. Finally, the challenges of Ni-MH batteries are discussed in the context of developing electric vehicles.