As electrical automobile adoption grows, the necessity for battery recycling is rising alongside with it. Typically, recycling includes breaking the battery down into pure chemical elements that may be reconstituted for brand-new battery materials. But what if—at least for some battery chemistries—that’s overkill?
A new research led by Panpan Xu at the University of California, San Diego reveals off a really completely different method for lithium-iron-phosphate (LFP) batteries. This isn’t essentially the most power-dense kind of lithium-ion battery, nevertheless it is economical and long-lived. (It’s the chemistry Tesla wants to rely on for shorter-vary autos and grid storage batteries, for instance.) Its low value cuts each methods—cheaper components imply much less revenue from recycling operations. But rejuvenating the lithium-iron-phosphate cathode materials with out breaking it down and beginning over appears to be potential.
The concept behind the research depends on information of how LFP battery capability degrades. On the cathode aspect, the crystalline construction of the fabric doesn’t change over time. Instead, lithium ions more and more fail to find their means again into their slots in the crystal throughout battery discharge. Iron atoms can transfer and take their place, plugging up the lithium pathway. If you possibly can persuade iron atoms to return to their assigned seats and repopulate with lithium atoms, you possibly can have cathode materials that is actually “as good as new.”
To check a technique for performing this reset, the researchers took industrial batteries and charged and discharged them till the batteries had misplaced half their capability. (A discount to 80 p.c capability is usually the outlined “end of life” marker.) Then the researchers disassembled the batteries and harvested the LFP cathode powder.
The first step is “relithiation”—bathing the powder for quite a few hours in a heated lithium answer that additionally included some citric acid. The heat temperature (round 80°C/175°F) and citric acid assist the iron atoms return to their houses in the crystalline lattice and assist the lithium ions pop again into place.
After washing and drying the powder, the workforce examined new cathodes made with the recycled materials. But while this confirmed “like new” capability, it degraded pretty rapidly. So the researchers added a second step in the method: annealing the dry powder at a lot increased temperatures.
Over a number of hours, the rejuvenated powder was heated to 600°C (1,112°F), held there for a while, and then cooled again down. This improved the order and stability of the crystalline construction in the powder particles, and the cathodes made after this course of held their capability identically to the brand-new ones by means of 300 cost cycles.
This “direct recycling” course of has a robust financial benefit over typical strategies. The researchers say it makes use of 80-90 p.c much less power and consequently is related with round 75 p.c much less greenhouse fuel emissions. For LFP batteries, the researchers estimate that hydrometallurgical processes (based mostly on dissolving materials and chemically separating them) run at a internet lack of round $1.40 per kilogram. Pyrometallurgical processes (which begin by melting every little thing) are even worse, costing round $2.60 per kilogram. But the researchers’ direct recycling course of can run at a revenue, producing barely over $1 per kilogram.
This method may not be restricted to LFP batteries, both. The researchers point out lithium-manganese-oxide chemistries, particularly, as a probable candidate. This is one other widespread kind of lithium-ion battery used in a spread of purposes.
As with any laboratory know-how, there will definitely be challenges to sort out in order to scale this to a industrial recycling plant. But if it may be completed, this approach might assist broaden the vary of batteries that may be recycled economically, lowering the reliance on mining to produce virgin materials.