Sustainable Upcycling of Spent Electric Vehicle Anodes into Solution-Processable Graphene Nanomaterials

Abstract

A major transition to electric vehicles (EVs) is underway globally, as countries target reductions in greenhouse gas emissions from the transport sector. As this rapid growth continues, significant challenges remain around how to sustainably manage the accompanying large volumes of waste from end-of-life lithium-ion batteries that contain valuable rare earth and critical materials. Here, we show that high-shear exfoliation in aqueous surfactants can upcycle spent graphite anodes recovered from an EV into few-layer graphene dispersions. For the same hydrodynamic conditions, we report a process yield that is 37.5% higher when using spent graphite anodes as the precursor material over high-purity graphite flakes. When the surfactant concentration is increased, the average atomic layer number reduces in a similar way to that of high-purity precursors. We find that the electrical conductance of few-layer graphene produced using the graphite flake precursor is superior and identify the limitations when using aqueous surfactant solutions as the exfoliation medium for spent graphite anode material. Using these nontoxic solution-processable nanomaterial dispersions, functional paper-based electronic circuit boards were fabricated, illustrating the potential for end-to-end, environmentally sustainable upcycling of spent EV anodes into new technologies.

Modification of kitchen blenders into controllable laboratory mixers for mechanochemical synthesis of atomically thin materials

“…Once processing has completed, and all nanomaterial has been removed from the batch, the precursor sediment can be recycled using a fresh batch of solvent/liquid dispersant. We have found that recycling this sediment using a second exfoliation run and fresh aqueous-surfactant solution can produce % of the initial 2DM output [28] . One can also try exfoliation in recovered solvents, or upcycling other layered precursor sources as Stafford and Kendrick showed in their recent paper on end-of-life Li-ion battery anode materials [28] .…”

“…This relationship ( ) breaks down at the extremes of precursor concentrations or when the liquid is sufficiently saturated [22] . Changes in surfactant concentration typically produce one maxima, though there are some outlier cases for lower purity graphite precursors [28] . Generally, only small amounts of surfactant are required for stabilising 2DMs, with anything above dropping off sharply, the maxima usually lying somewhere in this range [29] .…”

“…Optical extinction measurements were used to determine concentration (through the Lambert–Beer law) using a PerkinElmer Lambda 365 UV–vis Spectrophotometer, and a measured extinction coefficient of 1521 L g −1 m −1 at . The procedure for measuring the extinction coefficient is described in detail elsewhere [28] . …”

“…More recently, surfactant concentrations of mM were shown to be a critical point for concentration, length and thickness, irrespective of the surfactant choice or CMC [29] . LPE tends to produce nanosheets within large size distributions, though it is possible to reprocess any separated supernatant to reduce the average layer count [18] , [28] .…”