Recycling lithium-ion batteries for a brighter tomorrow
Australia's use of lithium-ion batteries (LIBs) is soaring. Their long lifespan, high efficiency and use across an increasing range of applications present benefits for consumers. But as demand grows, so too does the question of how we safely manage this waste stream.
It's a problem that our researchers across energy, minerals and manufacturing have been working hard to solve. Now, a recently constructed pilot facility for recycling LIBs is helping uncover crucial insights. Their discoveries have the potential to make the process much safer—not just in Australia but around the world.
Managing the challenges of lithium-ion battery waste
While it's possible to recycle LIBs at the end of their service life, it's a complex and costly process. As of 2021, only about 10% of Australia's LIBs were being recycled. Globally, that figure is about 5%.
There are several programs working to promote the collection, recycling and safe disposal of all batteries. These include the Australian Battery Recycling Initiative, of which we are a member, but there is a long way to go before LIBs reach the 98% recycling rate that has been achieved for lead acid batteries.
Dr. Thomas Ruether is a Senior Research Scientist and Team Leader with the Electrochemical Energy Storage team in our Energy Technologies Program. He says there are very, very few places in Australia that do LIB recycling.
"Due to government subsidies, enabling regulatory frameworks and larger volumes of end-of-life LIBs, about 90% of the world's recycling capacity is located in Asia and Europe, with a small amount also taking place in the U.S.," Thomas says.
"Previously, it was common practice in Australia to package our battery waste up and ship it overseas. However, this has become increasingly difficult because of the risks of end of service life LIBs. Much of it is now just warehoused by private industry."
Costs and complexities for domestic recycling efforts
Low recycling rates pose several different problems. If LIBs are not properly disposed of, there is risk that harmful materials may leach out of landfill sites resulting in environmental and health issues. Large, concentrated volumes of batteries stored in warehouses or scrap yards need careful management. This is due their flammable electrolyte systems and potential environmental contamination.
There are also sustainability considerations given LIBs contain concentrated high-value critical metals and minerals. If we don't recycle lithium-ion batteries, the valuable materials they contain are forgone. A shame when many of these materials can be reused in new batteries or repurposed for other applications. New raw materials will then have to be mined (which may be comparatively more economic to source).
In response to these challenges, our report, "Australian Landscape for Lithium-Ion Battery Recycling and Reuse in 2020," identified a range of opportunities across research, industry development, policy and regulation, to strengthen and grow Australia's domestic recycling capability.
We are currently engaged in several of these research opportunities. They address battery fire safety risks during collection, transportation, and storage. Additionally, there is a focus on research and development to support recycling lithium-ion batteries into high-value products. This includes second life reuse applications, economic recovery and utilization of battery electrolyte and graphite, and environmentally friendly recovery of battery metals.
Current battery recycling practices
When LIBs reach their end of service life and are collected for recycling, the initial step of the process is to shred them into smaller pieces for further processing.
Thomas reviewed battery market and recycling trends in a paper he co-authored in 2021, published in Sustainable Chemistry.
"LIBs are processed to a point where you recover what's called Black Mass," Thomas says.
"Black Mass is essentially graphite and metal oxides—the electrode materials—mixed together in a powder. It can be safely exported offshore for further processing to recover lithium, cobalt and nickel."
Depending on the processes used, between 50% and 95% of the materials contained in LIBs can be recovered. While the shredding of LIBs is routinely practiced in the recycling industry, there are still significant safety concerns and many unknowns relating to the risk of fire and explosion. There is also the potential release of toxic compounds.
Traditional aqueous wet shredding utilizes a submerged setting with a brine solution. To mitigate some of these risks, progressive recycling operations are moving away from aqueous wet shredding. Instead, they're opting for dry shredding under an inert gas blanket to keep air-oxygen out. The dry method also provides the benefit of recovering more recyclable material of value, safely.
For example, electrolyte salt is a small but valuable component of a battery. It represents about 2% to 3% of the electrolyte solution that makes up 15% of a battery cell mass. However, it accounts for more than 60% of the electrolyte solution cost.
In a wet shredding environment, the electrolyte solution reacts with water and decomposes. This results in toxic corrosive gas which needs significant effort to manage. However, in dry shredding it can be safely separated and potentially recovered.
Innovations in LIB recycling technology
Improving the safety of LIB recycling—and increasing Australia's capacity to undertake such processes—is an urgent priority. Our researchers are focused on two key areas.
"The first big problem for recyclers is the difficulty of determining what state of charge a battery is in," Thomas says.
"When LIBs come into a recycling facility for processing, they usually contain residual energy. This presents a significant hazard. If you get a short circuit, or they get damaged, they can cause a fire or explosion."
To address this, Thomas' team has worked in partnership with an e-waste recycler. They aim to develop an electrical discharge unit that allows for the safe and controlled discharging of batteries. The project is funded by the New South Wales Government EPA.
"During the discharge process you can develop heat, and you need to avoid the batteries going into a thermal runaway reaction," Thomas says.
A thermal runaway reaction leads to rapid temperature and pressure increase, often causing fire or an explosion.
"We monitor the temperature, current and voltage during the discharge process to ensure the discharge takes place in a controlled manner."
The second area of focus involves collecting data on the performance of dry shredding systems at an industrial scale and identifying operational limitations for safe processing.
Thomas' team has commissioned a pilot facility at our Clayton site for the safe dry shredding of LIBs under an inert nitrogen gas atmosphere (N2).
The plant, which can handle up to 10-kilogram batches of batteries, is a first of its kind in Australia. It is equipped with several technical features such as optical and thermal (IR) cameras, an additional airtight port for injecting single battery cells, and the ability to measure and clean the exhaust gases emitted from the process. It also includes a novel process to recover lithium electrolyte salt using the dry shredded material as a pure crystal which can be used for making new batteries. Patent protection is being sought for the process.
"The plant is ideally suited to on-site monitoring and data collection during the processing of LIBs," Thomas says.
"We can do optical and thermal monitoring of what's occurring in the shredding chamber. So, you can see very clearly on the video footage what can happen depending on how much energy is left in the batteries."
"These insights into what takes place during the dry shedding process are hugely important. Not just to our own research and process development, but also to the battery recycling industry globally as they address serious safety concerns and many unknowns concerning materials integrity and their further downstream processing."
Provided by CSIRO