The widespread consumption of electronic devices has made spent batteries an ongoing economic and ecological concern with a compound annual growth rate of up to 8% during 2018, and expected to reach between 18% and 30% to 2030. There is a lack of regulations for the proper storage and management of waste streams that enables their accumulation in o. Legacy of battery contaminantsBattery nanomaterial-wasteBattery ecotoxicological effectsBattery recycling solutionsNanowasteE-wasteThe growth of e-waste streams brought by accelerated consumption trends and shortened device lifespans is poised to become a global-scale environmental issue at a short-term, i.e., the electromotive vehicle industry with its projected 6 million sales for 2020 [, ]. Efforts for the regulation and proper management of electronic residues have had limited impact due to the lack of accountability and low economic viability of recycling facilities. Consequently, a large proportion of electronic equipment is discarded to landfills, where its toxic components are released into the environment.As the main source of electricity for a broad range of devices, batteries are a significant contributor to total generated e-waste. The most used battery types contain considerable quantities of heavy metals like manganese, lead, cadmium, and lithium and other currently identified contaminants widely regarded with high ecotoxicity (Table 1) [6,7]. Furthermore, the small sizes and different compositions between batteries contribute to their improper disposition and make recycling difficult.Table 1. Current and emerging contaminants found on batteries and their ecotoxicological effects.The. 2.1. Metal nanostructuresOver the past decade, primary and secondary batteries have migrated from bulk materials into nanostructures derived from transition metal phosphates and metal oxides for their cathode, anode, and electrolyte components. The transition towards emerging trends of manufacture has been driven by the reported enhanced electrical capabilities of developed batteries (higher capacity and throughput and longer lifespan), enabling the consumer adoption of energy storage as a low-cost gateway towards widespread energetic accessibility on communities not connected to the electric distribution grid. The main features, and environmental challenges, of the transition towards emerging manufacturing of batteries are summarized on Fig. 1. Metal nanostructures achieve higher rates of lithium intercalation/deintercalation, and the increased superficial area improves electrolytic contact. The novel features presented by materials technology are translated into increases of the storage capacity and the energetic efficiency of batteries. Currently, these innovations have reached their implementation on vehicles and large-scale storage for domestic settings. The application of metal nanostructures into batteries, from nanoparticles to full-fledged 3D arrays, has also boosted the global demand for the manufacture of nanomaterials based on metals exponentially.3.1. Risk assessment of battery nanomaterialsGiven the emerging nature of nanomaterials applied for battery enhancement, the characterization of their effects on human health and environment poses unique challenges, as the limited scope of their implementation hampers assessment guidelines of broad relevance. The lack of standardized methods to model nanowaste life-cycle, morphology and particle size distribution also prevents the critical comparison of toxicity effects between nano-scale and bulk materials. The considerable uncertainty of the safe usage of nanomaterials at a wide scale has left a governance gap as the looming large scale adoption outpaces the ability to adjust current regulation according to available studies. The application of risk assessment (RA) for nanomaterials thus takes relevance in the context of battery mass production to support evidence of their safety and bring certainty on the environmental consequences of the disposal of end-of-life products.Risk assessment refers to the qualitative and quantitative estimation of the negative environmental effect that the exposure to a substance may pose, as well as the socioeconomic consequences of such exposure. Robust RA strategies for nanomaterials must consider an integral characterization of the physicochemical properties of the studied substance as a cornerstone for life cycle hazard modelling. These.
