The recent developments in EV batteries and REEs recovery processes from spent NiMH batteries

Electric vehicles (EVs) are becoming more popular than internal combustion engines for reasons such as ease of use, durability, efficiency, and speed. Electric motors aim to improve the efficiency of energy storage systems and be more environmentally friendly. Due to the growing population, the number of vehicles in use is also increasing, leading to higher carbon dioxide (CO2) and hydrocarbon emissions. This demand has positively affected the battery market in the EV industry. Battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), along with lead-acid batteries, nickel–metal hydride (NiMH) batteries, and lithium-ion batteries, are frequently preferred in the EV industry. NiMH batteries contain approximately 35–50% nickel (Ni), 5–20% rare earth elements (REEs), and 10% iron (Fe) by weight. Considering the supply and demand gap for REEs, often called “vitamins of modern industry”, the recovery of REEs from waste NiMH batteries, which contain high amounts of these elements, becomes important. In this review article, literature on EVs, their types, and EV battery types is presented. In addition, the recycling process of NiMH batteries, which are very rich in REEs and precious metals, such as Ni, cobalt (Co), and manganese (Mn), is discussed, and the enrichment methods effective in the recycling process of NiMH batteries are examined.