Using life cycle assessment to aid process development for hydrometallurgical recycling of end-of-life lithium ion batteries

Abstract

The global stockpile of recyclable end-of-life (EOL) lithium-ion batteries (LIBs) is continuously increasing in size, while hydrometallurgical processes are starting to play an increasingly important role in EOL LIB recycling. To this end, this study aims to use life cycle assessment (LCA) to aid the process development of hydrometallurgical LIB recycling using hotspot analysis. The LCA investigation started by comparing three lixiviants (hydrochloric-, sulphuric-, and citric acid) and three metal recovery strategies (mixed precipitation, selective/sequential precipitation, and integrated solvent extraction-precipitation) using the ReCiPe H/H method. The sulphuric acid - mixed precipitation process was found to be the most environmentally friendly based on endpoint value. Across these nine different processes there were 633 midpoint hotspots identified with 64.3% originating from the hydrometallurgical recovery circuit, 20.5% from the leaching process and 10.7% from the dense media separation of copper and plastic in pretreatment. Pneumatic separation of copper and plastic was then proposed to replace dense media separation which led to a 14.3% decrease in the endpoint value of the pretreatment section. Subsequently, formic acid leaching and nanofiltration were suggested as solutions to the hotspots relating to leaching and metal recovery. The study then showed that formic acid leaching could potentially increase cobalt recovery (compared to sulphuric acid leaching) by 2.1%. Furthermore, utilising nanofiltration to aid metal recovery was found to potentially decrease sodium hydroxide and process steam consumption by 54.6% and 68.8% respectively.