One of the difficulties faced by lithium battery recycling is that the cost of the material itself is low, but the recycling process is not cheap. A new technology hopes to boost the recycling of lithium batteries by further reducing costs and using environmentally friendly components.
A new processing technique that returns spent cathode material to its pristine state could further save lithium-ion battery recycling costs. The technique, developed by nanoengineers at the University of California San Diego, is more environmentally friendly than methods used today. It uses greener ingredients, consumes 80% to 90% less energy, and emits 75% less greenhouse gas.
In a paper published Nov. 12 in Joule, the researchers detailed the findings.
The treatment works particularly well for cathodes made of lithium iron phosphate, or LFP for short. LFP cathode batteries are less expensive than other lithium-ion batteries because they do not use precious metal materials such as cobalt or nickel. LFP batteries also last longer and are safer. They are widely used in power tools, electric buses and power grids. Tesla Model3 also chose LFP batteries.
"Given the above advantages, LFP batteries will have a competitive advantage over other lithium-ion batteries on the market," said Zheng Chen, professor of nanoengineering at UC San Diego.Also read:catl lifepo4
So what's the problem? "The battery isn't cost-effective to recycle," Chen said. "It's in the same dilemma as plastic—the material itself is cheap, but the recycling method isn't cheap."
The new recycling technology developed by Chen and his team could reduce these costs. The technology works at low temperatures (60 to 80 degrees Celsius) and ambient pressure, thus using less power than other methods. In addition, the chemicals it uses, such as lithium salts, nitrogen, water and citric acid, are cheap and mild.
"The whole process of recycling takes place under very safe conditions, so we don't need any special safety precautions or special equipment," said Panpan Xu, the study's first author and a postdoctoral researcher in Chen's lab. The reason for the low cost of battery recycling.”
First, the researchers cycled the LFP battery repeatedly until the battery lost half of its energy storage capacity. They then disassembled the battery, collected the cathode powder, and soaked it in a solution containing lithium salts and citric acid. Next, they rinsed off the solution with water and allowed the powder to dry before heating it.
The researchers used these powders to make new cathodes, which they tested in both coin cells and pouch cells. Their electrochemical performance, chemical composition, and structure were all fully restored to their initial states.
As the battery is continuously cycled, the cathode undergoes two important structural changes that degrade its performance. The first is the loss of lithium ions, which create cavities in the cathode structure. Second, another structural change occurs when the iron and lithium ions in the crystal structure switch places. Once this change occurs, the position of the ions cannot be easily switched back, so the lithium ions become trapped and can no longer cycle through the battery.
The treatment method proposed in this study first replenishes lithium ions, allowing iron ions and lithium ions to easily switch back to their original sites, thereby restoring the cathode structure. The second operation is achieved by using citric acid, which acts as a reducing agent, donating electrons to another substance. It transfers electrons to the iron ion, reducing the positive charge it carries. This minimizes electron repulsion, preventing the iron ions from moving back to their original sites in the crystal structure, while releasing the lithium ions back into circulation.
While the overall energy consumption of this recycling technique is lower, the researchers say further research is needed to understand the logistics of collecting, transporting and disposing of large quantities of batteries.
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