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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.

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Eutectic mixtures of zinc chloride and donor molecules such as urea and acetamide are described and it is proposed that these constitute a new class of ionic liquids. FAB-MS analysis shows that the liquids are made up of metal-containing anions and cations in which the donor is coordinated to the cation. Data on the viscosity, conductivity, density, phase behaviour and surface tension are presented and these are shown to be significantly different to other related ionic liquids that incorporate quaternary ammonium salts. The conductivity and viscosity are comparable with other ionic liquids and the data fit well to the Hole theory model recently proposed.

Eutectic mixtures of quaternary ammonium salts with Lewis or Brønsted acids have been described as ionic liquid, but doubt exists over the compositional range for which this description is valid. In the current work, the conductivity, viscosity, density, and surface tension of a number of glycolic mixtures with choline chloride are measured over the mole fraction range 0 to 0.33. The data are fitted to hole theory, and it is proposed that the composition at which the measured conductivity matches the theoretical value is the point at which hole mobility becomes the dominant mechanism for charge mobility. For the mixtures of ethylene glycol and butanediol, this occurs at a ChCl mole fraction of approximately 0.2.

Here we describe for the first time the electrolytic deposition of copper and copper composites from a solution of the metal chloride salt in either urea-choline chloride, or ethylene glycol-choline chloride based eutectics. We show that the deposition kinetics and thermodynamics are quite unlike those in aqueous solution under comparable conditions and that the copper ion complexation is also different. The mechanism of copper nucleation is studied using chronoamperometry and it is shown that progressive nucleation leads to a bright nano-structured deposit. In contrast, instantaneous nucleation, at lower concentrations of copper ions, leads to a dull deposit. This work also pioneers the use of the electrochemical quartz crystal microbalance (EQCM) to monitor both current efficiency and the inclusion of inert particulates into the copper coatings. This technique allows the first in situ quantification or particulate inclusion. It was found that the composition of composite material was strongly dependent on the amount of species suspended in solution. It was also shown that the majority of material was dragged onto the surface rather than settling on to it. The distribution of the composite material was found to be even throughout the coating. This technology is important because it facilitates deposition of bright copper coatings without co-ligands such as cyanide. The incorporation of micron-sized particulates into ionic liquids has resulted, in one case, in a decrease in viscosity. This observation is both unusual and surprising; we explain this here in terms of an increase in the free volume of the liquid and local solvent perturbation.

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