Resource scarcity is a growing concern in battery production. Recycling lithium from spent batteries could help, and new research makes it easier.
Batteries play a key role in today’s dynamic energy transition process. The increasing demand for batteries in numerous applications, especially for the electric vehicle (EV) industry, is putting pressure on our limited supply of battery materials like lithium. The scarcity of these materials undermines the goal of making green solutions widely available and affordable.
Can we mine enough battery material to make a successful energy transition? It depends on how well we can recycle.
There are several current processes for recycling battery materials, which mainly adapt existing processes used to purify other metals. However, these technologies are not efficient enough for large scale battery recycling. Developing a greener and more efficient approach to battery recycling is an urgent priority to address resource management and environmental pressures.
The global urgency of battery recycling
World reserves of key battery materials, such as lithium and cobalt, are limited and dependent on a few countries. For example, over 70% of cobalt production—and more than half the world’s cobalt reserves—is found in the Democratic Republic of Congo. Australia, Chile and China together accounted for 90% of world’s lithium production in 2021.
It gets worse. The mining of key battery materials uses significant amounts of water and energy. It pollutes the air and water with chemicals and heavy metals, leading to long-term ecological damage. Discarded batteries contain toxic substances that are also very harmful to the environment. The International Energy Agency (IEA) estimates that EVs manufactured in 2019 alone generated 500,000 tons of battery waste, and that number could reach 8 million tons by 2040.
As crucial as batteries are to the energy transition, it is even more crucial to find better ways to produce them. Recycling batteries will be key, and it’s becoming a political priority. The EU, for example, recently released regulation concerning batteries and waste batteries with clear and optimistic goals for battery recycling. Recycling efficiency is crucial. The regulation targets a recycling efficiency goal of 70% by the average weight of lithium-based batteries no later than December 31, 2030. The recycling efficiency of individual materials is set at 95% for cobalt and 80% for lithium.
To achieve those goals, we’ll need to find better ways to recycle batteries—and fast.
The challenges of lithium-ion battery recycling
Recycling lithium-ion batteries, the most common type today, is a difficult undertaking. The recovery of high-quality lithium is complex and expensive.
Current recycling methods extract lithium from cathodes, where lithium is stored when the battery is discharged. The challenge with this approach is that the lithium is mixed up with other metals contained in the cathode, making its extraction complicated. Additionally, before crushing, the batteries must be discharged completely to zero volts, a challenging, time-consuming process requiring proper equipment. Otherwise, battery short circuits during smashing can result in arcing, flashing and fire.
Discharging down to zero volts necessitates advanced controllable discharging systems to provide a full discharge in a reasonable time. If done with simple resistors, the current decreases as the voltage decreases, causing the discharging process to take too long. Even if the batteries are discharged to zero volts, when disconnected, the voltage will recover. A battery recycling approach that skips this zero-discharging step would be highly beneficial.
The anode provides a safer approach to extracting lithium
An alternative approach is to extract lithium from the battery’s anode rather than the cathode. Since the anode primarily contains graphite, it would be easier to separate the lithium metal. Additionally, this approach could avoid the deep discharging before the recycling process.
However, anode extraction presents its own problems. Leaching the anodes with commonly used aqueous solutions poses a high risk of fires and explosions, due to battery reactivity that releases large amounts of energy and generates hydrogen.
To get around that problem, a research team from China recently published their work on a promising new approach to anode extraction. Instead of water, the team used aprotic organic solutions to recover lithium from anodes. These substances cannot release any hydrogen ions, which eliminates the potential for flammable hydrogen gas to form. The proposed solution includes polycyclic aromatic hydrocarbon (PAH) and ether (tetra-ethylene glycol dimethyl) as the solvent.
The researchers, from the Institute of Chemistry of the Chinese Academy of Sciences (ICCAS) and the University of Chinese Academy of Sciences (UCAS), published their work in August 2023 in Angewandte Chemie. They say their redox reaction is controllable and efficient under mild conditions, ensuring a safe and efficient recycling process with almost 100% active lithium recovery from the anodes. The resulting lithium solution can be used directly as a reagent in the preprocessing of new anodes, and also in the regenerating process of spent cathodes.
On the right recycling track
We have a long way to go in our necessary energy transition, but the collective efforts of engineers and scientists around the globe are starting to make a difference. Better battery recycling is but one technical hurdle we need to overcome—but it has the potential to make an outsized impact if we can overcome its challenges.
For more on battery recycling, check out these other stories on engineering.com:
The Who’s Who of Lithium-ion Battery Recycling
Battery Recycling Technologies – Part 1: Introduction and Recycling Preparation
