Is it possible to extract metals from a lithium battery in half the time it normally takes?
Is it possible to use acids that are common in most homes worldwide for the extraction process?
The answer is yes. Scientists at KTH have discovered a way.
Known by expectant parents as the technology that enables them to see their child for the first time, ultrasound can be used at extremely low frequencies to serve an entirely different purpose.
Researchers at KTH Royal Institute of Technology in Sweden report the first ultrasound extraction of valuable metals from electric car NMC batteries – a key contribution to the battery recycling process.
Not only does the new method add ultrasonic waves to the process of extracting metal ions from destroyed batteries, it also offers an alternative to the current use of harmful leaching agents – such as sulfuric acid.
The payoff is a 50 percent reduction in extraction time and an increased recovery of metal ions such as lithium, cobalt, manganese, and nickel, says Xiong Xiao, a researcher in polymeric materials at KTH.
“The benefits will extend beyond electrification of automobiles to countless systems that rely on sustainable energy storage – from mobile phones to electrical grids.”
Ultrasonic baths send waves of mechanical pressure with extremely high frequencies. In this case, the researchers used a frequency of 40kHz – a tone far beyond the hearing range of humans. These waves create microbubbles that collapse, generating local temperatures of nearly 5,000C, and producing highly reactive free radicals.
Instead, gentler, environmentally safe acids such as citric and acetic acid can be used, Xiao says.
As reported in the journal Green Chemistry, the method achieved on average 97 percent metal ion recovery, which was a substantially higher amount of recovered metal ions than for the same conditions when only mechanical stirring was used. The highest recoveries were achieved for cobalt and nickel, reaching more than 99 percent, while lithium and manganese were recovered with 94 to 96 percent efficiency.
“With ultrasound Xiong Xiao has discovered a way to eliminate the need for chemicals normally used, such as strong acids that are nearly unmanageable,” says Richard Olsson, co-author and lecturer at the Division of Polymeric materials at KTH.
Xiao’s work is a part of PERLI (Process for Efficient Recycling of Lithium Ion Batteries) project 48228-1 financed by The Swedish Energy Agency. The research was carried out in collaboration with battery manufacturer Northvolt.
Ultrasonics Makes Lithium-Ion Battery Recycling More Efficient
Lithium is a scarce and highly valuable material present in high-performance batteries, such as Li-ion batteries. Lithium is the most valuable material that is recovered in Li-ion battery recycling, but also other minerals and metals such as cobalt, manganese, nickel, copper and aluminum are valuable metals for recovery. High-intensity ultrasonication is used as high-shear agitation and leaching technique to extract, remove, and dissolve valuable minerals and metals from spent batteries.
The sonication method is highly efficacious, energy-efficient, and is readily available for installation in full-commercial recycling facilities. Overview: The Li-Ion-Battery Recycling Process The recycling processes may vary as companies specialising in Li-ion battery recycling develop and modify their processes to highest efficiency.
However, in order to recover valuable materials such as lithium from the batteries, following steps are required: First, the plastic cover of the battery is broken up and removed. Afterwards, the naked battery is put in liquid nitrogen in order to neutralise reactive, explosive substances.
This step makes sure that a sudden release of all stored energy and the subsequent ignition and explosion associated with are prevented. After these preparative steps, the battery is then placed on a lathe, where the battery is opened with a saw, so that the outer shell can be removed. Stripped down to the battery’s core, the cathode, anode, and separator are extracted and placed in an oven, where they are dried for 24 h at approx. 60-120°C.
Before the metal-extraction treatment, the isolated electrodes, i.e. cathode and anode, must be further disassembled. Since the cathode material is generally adhered to aluminum foil by a binder, commonly polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), it is a difficult task to remove cathode and aluminum foil from each other.
To properly separate the cathode material from the foil, the ultrasonic separation has been proven to be a highly efficient, rapid, and economical treatment. But the ultrasonic process intensification does not stop here. Ultrasonic leaching of metals and minerals such as cobalt, manganese, nickel, copper and aluminum promotes the metal extraction and increases the yield of recovered metals.
Ultrasonics for the Highly Efficient Recovery of
- Lithium
- Cobalt
- Manganese
- Nickel
- Copper
- Aluminium
- LiCoO2
- Graphite
Ultrasonic Cavitation for Cathode Separation
Ultrasonication separates cathode materials from aluminum foil by the effects of acoustic cavitation. Acoustic or ultrasonic cavitation is determined by locally occurring high pressures, high temperatures and their subsequent drops resulting in respective pressure and temperature differentials as well as intense micro-turbulences and high-shear micro-jets. These cavitational forces affect surface boundaries, promote mass transfer and cause erosion.
Generating such intense forces of chemical, physical, thermal and mechanical nature, ultrasonic cavitation creates the required agitation and mass transfer to break the organic binder structure used in lithium-ion batteries to fixate the cathode to the collector / aluminum foil.
Whilst mechanical agitation such as stirring alone is insufficient to detach the cathode material effectively from the aluminum foil, high-intensity ultrasonication provides the required sonochemical and sonomechanical energy to remove the cathode material completely from the collectors.
In contrast to mechanical stirring, ultrasonic cavitation generates intense turbulences, locally high temperatures and pressures as well as agitation, streaming and liquid jets, which break up the binder, e.g. PVDF or PTFE, which connect the cathode to the Al foil, and erodes the surface of both, cathode and Al foil. Thereby, the binder between both materials is properly destructed and cathode and aluminum foil are effectively separated.
For instance, ultrasonic separation results in high efficiency of the cathode removal of 99% using N-methyl-2-pyrrolidone (NMP) as solvent at 70°C (240 W ultrasonic power, and 90 min ultrasonic processing time). Since ultrasonic cathode separation disperses the material evenly and prevents larger agglomerates, the subsequent metal leaching process is facilitated.
Ultrasonic Leaching of Minerals
The ultrasonic cavitational effects described above promote the leaching of metals from spent batteries, too. High-intensity ultrasonication is not only used to recover mineral in battery recycling, but is also often used in hydrometallurgy and the leaching of precious ores (e.g. mining tailings).
The high localized temperatures, pressures, and shear forces intensify the metal leaching and increase leaching efficiency significantly. Whilst in the cavitational hot-spots occur localized very extreme temperatures of up to 1000 K, the overall leaching conditions require only mild temperature of approx. 50-60°C. This makes the ultrasonic metal recovery energy efficient and economical.
Ultrasonic leaching of minerals from spent Li-ion batteries is characterized by high recovery rates and efficiency. For instance, sulfuric acid (H2SO4) was successfully used as leaching agent in the presence of hydrogen peroxide (H2O2) during ultrasonic mineral recovery from the cathode. Ultrasonic leaching with sulfuric acid resulted in recovery rates of 94.63% for cobalt, and 98.62% for lithium, respectively.
Ultrasonic leaching with organic citric acid (C6H8O7·H2O) results in very high recoveries of copper and lithium, obtaining 96% copper and nearly 100% lithium from the spent Li-ion batteries.
Advantages of Ultrasonic Battery Recycling
- High efficiency
- Established technique
- Simple operation
- Low / non-toxic solvent use
- Almost no exhaust emission / CO2 footprint
- Safe E
- nvironmental-friendly
reference link :https://www.hielscher.com/ultrasonics-makes-lithium-ion-battery-recycling-more-efficient.htm
More information: Xiong Xiao et al, Ultrasound-assisted extraction of metals from Lithium-ion batteries using natural organic acids, Green Chemistry (2021). DOI: 10.1039/D1GC02693C
