Why recycle batteries
Spent lithium-ion batteries contain lithium, nickel, cobalt, manganese, copper, aluminium and graphite, much of it in higher concentration than in natural ores. Recycling reduces the need for new mining and the risk of fires and pollution from discarded cells. Harper and co-workers (2019) reviewed the main routes and the challenges of recycling electric-vehicle batteries at scale.
Before recycling
- Discharge the cells safely, for example through a resistor or in a salt solution, to avoid short circuits and fires.
- Dismantle packs into modules and cells, and recover casings and electronics.
- Shred and separate to obtain the black mass, a mixture of electrode powders, separated from foils and plastics.
The main recycling routes
| Route | How it works | Strengths and limits |
|---|---|---|
| Pyrometallurgy | Smelting at high temperature into an alloy of Co, Ni and Cu | Robust and established, but energy-intensive, and lithium and aluminium end up in the slag |
| Hydrometallurgy | Leaching the black mass with acid, often with a reductant, then separating the metals by precipitation, solvent extraction or ion exchange | High recovery of Li, Ni, Co and Mn, with chemical and wastewater costs |
| Direct recycling | Recovering the cathode material and restoring its lithium and structure | Keeps the value of the engineered material, but needs well-sorted feedstock |
Upcycling into functional materials
Instead of returning every element to battery grade, part of the black mass or the leach solution can be turned directly into new functional materials. Mixed Ni, Co and Mn compounds are good starting points for oxygen evolution catalysts, layered double hydroxides, supercapacitor electrodes or high-entropy oxides, and graphite from spent anodes can become graphene-like supports. This is a central theme of our group.
- Characterise the feedstock first, for example by ICP for the metal ratio, and track impurities such as Al, Cu, Fe and residual fluoride, which change catalytic behaviour.
- Compare the upcycled material with one made from pure precursors of the same composition, so that the effect of impurities is clear.
- Report activity and stability with the same care as for any catalyst (Lesson 2.2), and include the yield and, where possible, a simple estimate of chemicals and energy used.
Safety in the lab
Spent cells can still hold charge and contain flammable electrolyte and LiPF6, which can release HF with moisture. Discharge before opening, open cells only in a fume hood with proper protection, and leach black mass in the fume hood, since acid leaching with reductants can release gases. Members of our lab should also follow members lesson 1 on lab safety.
Check your understanding
Quiz for lesson 6.3
Pick one answer per question. You see the explanation straight away.
References and further reading
- G. Harper et al., Recycling lithium-ion batteries from electric vehicles, Nature 575 (2019) 75–86. doi:10.1038/s41586-019-1682-5
- L. Gaines, The future of automotive lithium-ion battery recycling, charting a sustainable course, Sustain. Mater. Technol. 1–2 (2014) 2–7.