Simulation-based life cycle assessment for hydrometallurgical recycling of mixed LIB and NiMH waste

Abstract

The sustainable and competitive recovery of materials from spent batteries is becoming an urgent issue due to the increasing popularity of hybrid and fully electric vehicles. In this present study, flowsheet simulation was combined with life cycle assessment to investigate the environmental impacts of a conceptual, experimentally proven hydrometallurgical battery recycling process, where nickel metal hydride (NiMH) battery waste is used as reductant for lithium-ion battery (LIB) waste, synergistically improving the extraction of valuable metals from both waste types. Various options for sodium circulation in the precipitation of rare earths were considered in different scenarios. The results showed that the main benefit of the process was the reduced consumption of leaching chemicals. Of the investigated sodium management scenarios, crystallization of sodium sulfate was found to be the most environmentally feasible option, allowing the use of Na as a precipitation chemical for rare earth recovery. Significant potential reductions in climate change, acidification, freshwater eutrophication, and human toxicity were also achievable when compared to the life cycle impacts of the primary production of battery metals, mainly due to the high environmental footprint of primary nickel and cobalt sulfate production. Although further improvements to the process were found to be possible, the future availability of waste NiMH batteries may limit the application of the described process concept on an industrial scale.