The recycling of Li-ion battery anode material using supercritical solvents

Sudron, Samuel (2022). The recycling of Li-ion battery anode material using supercritical solvents. University of Birmingham. M.Res.

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Abstract

This research looks at the use of supercritical solvents on the potential of recycling the anode material from electric vehicle batteries. The anode material is made up of 5 layers; graphite, polyvinylidene Fluoride (PVDF), Copper, another layer of PVDF and another layer of graphite. This research looks at separating those layers using super critical fluid. The extraction of PVDF from between the copper and graphite, within the anode material, was done using a variety of solvents at supercritical conditions within a high-pressure vessel. The solvents used were acetone, methanol, ethanol, propanol, butanol, and dichloromethane (DCM). Acetone at these supercritical conditions self-reacted to produce iso�phorone. This caused the liquid to turn yellow due to the dissolved orange wax (iso-phorone). The alcohols all extracted the PVDF, this was tested using XRF, TGIR, Light Microscopy and SEM. A pattern was discovered that as the alcohol molecules C-number increased, so did the size of the PVDF particles and decreased the oxygen contaminant from 15% using methanol to 2% with butanol. This was concluded to be due to a decreased amount of depolymerisation taking place. The DCM produced a laminated PVDF product but included a graphite contaminate. Particles of PVDF being present due to it becoming dissolved in the solution at supercritical conditions and then precipitating during the cooling period of the vessel outside of the anode material.

Graphene was also produced using Supercritical fluids in a larger vessel with the help of a quick pressure release system. Graphene was produced using new and end-of-life graphite. Better results were found using end-of-life graphite, possibly due to the intermolecular forces becoming weakened over battery use. This may also produce a thinner and increase concentration of graphene. The use of ultra-sonic probe was inconclusive, further tests are required. Using this experimentation, a design for a continuous PVDF recovery was conceptualised for upscaled recycling in the future.

Type of Work:

Thesis (Masters by Research > M.Res.)

Award Type:

Masters by Research > M.Res.

Supervisor(s):