Experimental and economic-environmental analysis of bipolar membrane electrodialysis in lithium-ion battery recycling

Electrodialysis is gaining interest as an environmentally friendly refining method in the recycling of lithium-ion batteries (LIBs), referring to its low chemical demand with minimal formation of residual products. One commonly researched application is salt splitting, relying on bipolar membrane electrodialysis (BPED). It transforms salts like sodium or lithium sulfate into corresponding alkalis and acids – sodium or lithium hydroxide and sulfuric acid, enabling product recovery and zero liquid discharge by reagent recirculation. Despite frequently being referred to as sustainable, holistic views of the process jointly looking at environmental and economic considerations have rarely been reported in literature. This study evaluates a BPED process in a flowsheet for the recycling of LIBs based on black mass leaching and selective precipitation, where BPED was used to treat the residual salt solution upon metal recovery. The process was evaluated through experiments, life cycle assessment and cash flow analysis, with comparisons to alternative recovery and disposal options. It was found that BPED could be viable in geographies with abundant supply of fossil-free electricity, lowering the impact on, for example, global warming and ecotoxicity. Electricity is the main cash outflow, requiring low energy prices to make BPED economically justifiable. A positive net present value when investing in the studied process necessitates either an energy price of 0.035 USD/kWh, 35 % reduced membrane costs or 25 % increased prices for input chemicals than in the standard scenario. The economic-environmental sustainability greatly depends on the marketability of the Glauber’s salt recovered in alternative processing options.