Range of recycling technologiesRecycling Complexity of process 'Mixing' of materials streams Amount of materials recovered Value of materials recovered Fig. 1 | The waste management hierarchy and range of recycling options. The waste management hierarchy is a concept that was developed from the Council Directive 75/442/EEC of 15 July 1975 (https://eur-lex.europa.eu/legal-content/ EN/TXT/?uri=CELEX%3A31975L0442) on waste by the Dutch politician Ad Lansink, in 1979, who presented to the Dutch parliament a simple schematic representation that has been termed 'Lansink's Ladder', ranking waste management options from the most to least environmentally desirable options.Here, that hierarchy is expanded to consider the range of battery recycling technologies. 'Prevention' means that LIBs are designed to use less-critical materials (high economic importance, but at risk of short supply) and that electric vehicles should be lighter and have smaller batteries. 'Re-use' means that electric-vehicle batteries should have a second use. 'Recycling' means that batteries should be recycled, recovering as much material as possible and preserving any structural value and quality (for example, preventing contamination). 'Recovery' means using some battery materials as energy for processes such as fuel for pyrometallurgy. Finally, 'disposal' means that no value is recovered and the waste goes to landfill.

The market dynamics, and their impact on a future circular economy for lithium-ion batteries (LIB), are presented in this roadmap, with safety as an integral consideration throughout the life cycle. At the point of end-of-life, there is a range of potential options – remanufacturing, reuse and recycling. Diagnostics play a significant role in evaluating the state of health and condition of batteries, and improvements to diagnostic techniques are evaluated. At present, manual disassembly dominates end-of-life disposal, however, given the volumes of future batteries that are to be anticipated, automated approaches to the dismantling of end-of-life battery packs will be key. The first stage in recycling after the removal of the cells is the initial cell-breaking or opening step. Approaches to this are reviewed, contrasting shredding and cell disassembly as two alternative approaches. Design for recycling is one approach that could assist in easier disassembly of cells, and new approaches to cell design that could enable the circular economy of LIBs are reviewed. After disassembly, subsequent separation of the black mass is performed before further concentration of components. There are a plethora of alternative approaches for recovering materials; this roadmap sets out the future directions for a range of approaches including pyrometallurgy, hydrometallurgy, short-loop, direct, and the biological recovery of LIB materials. Furthermore, anode, lithium, electrolyte, binder and plastics recovery are considered in the range of approaches in order to maximise the proportion of materials recovered, minimise waste and point the way towards zero-waste recycling. The life-cycle implications of a circular economy are discussed considering the overall system of LIB recycling, and also directly investigating the different recycling methods. The legal and regulatory perspectives are also considered. Finally, with a view to the future, approaches for next-generation battery chemistries and recycling are evaluated, identifying gaps for research.

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