Low-Temperature Magnetic Recycling of Spent Lithium Iron Phosphate Cathodes

Lithium iron phosphate (LiFePO₄) batteries are widely used because they are safe, long-lasting, and relatively affordable. When these batteries reach the end of their life, recovering valuable materials is important. Before the cathode material can be reused, however, it must first be separated cleanly from the rest of the electrode, especially the aluminum foil. Conventional recycling generally relies on pyrometallurgical or hydrometallurgical processing. High-temperature routes consume substantial energy and can produce material mixtures that still require further separation. Wet chemical processes can achieve high recovery efficiencies, but they depend on considerable amounts of chemical reagents. For LiFePO₄ batteries, improving the pretreatment stage could reduce the burden placed on these later processing steps by recovering a cleaner cathode material before chemical or high-temperature treatment becomes necessary.

Magnetic separation offers an appealing physical alternative because LiFePO₄ is magnetic, unlike several other components found in the battery. The difficulty appears when entire electrodes are crushed into fine particles before separation. LiFePO₄ particles can become mixed with non-magnetic aluminum, copper, and graphite through particle agglomeration and electrostatic interactions. The magnetic field then collects material that is not purely LiFePO₄, reducing the quality of the recovered fraction. Making the particles increasingly fine can worsen this problem rather than solve it.

A second challenge remains even after cathode and anode components have been distinguished. In the cathode sheet, LiFePO₄ is bonded strongly to aluminum foil by polyvinylidene fluoride, or PVDF. This polymer performs an essential function during battery manufacture and use, but during recycling it becomes an obstacle: the active material cannot be recovered cleanly until the binder has been sufficiently decomposed. Heating can remove PVDF, yet excessive temperature or treatment time can damage the aluminum collector and introduce aluminum into the recovered cathode material.

In a recent paper published in ACS Sustainable Resource Management, Dr. Cheng Gong, Professor Meizhou Qi and Professor Wentuan Bi from the Institute of Energy at Hefei Comprehensive National Science Center, together with Chenxi Su and Professor Yulun Tao from Anhui University of Science and Technology, developed a cascaded recycling process for spent LiFePO₄ batteries. Their approach combines dry magnetic separation with controlled heating to recover and regenerate the cathode material.

Instead of grinding the electrodes into a fine powder, the team kept them in larger pieces and used magnets to separate the cathode and anode. This helped prevent the materials from mixing and made it easier to recover purer LiFePO₄. The next step was to detach the LiFePO₄ from the aluminum foil. The researchers used controlled heating to break down the PVDF binder that holds the active material to the current collector. They found that moderate heating was sufficient to weaken this adhesive layer and release the cathode material. If they used excessive heating, they noted it can damage the aluminum foil and introduce contamination into the recovered LiFePO₄.

The authors observed that the best separation was achieved at about 400 °C for six hours. Under these conditions, the cathode material detached cleanly and the aluminum foil remained largely intact. The process recovered more than 97% of the LiFePO₄ with a purity above 99%, at a much lower temperature than many conventional thermal recycling methods. The recovered material still required regeneration because lithium had been lost during battery cycling. The team tested two lithium sources and found that lithium carbonate gave the better result. After relithiation, structural measurements showed that the LiFePO₄ crystal lattice was largely restored and that the chemical state of iron moved back toward that expected in regenerated material.

Electrochemical testing showed that the regenerated material also worked well as a battery cathode. Its discharge capacity was close to that of commercial LiFePO₄, and it remained stable over repeated charge and discharge cycles. Charge transfer was also much easier than in the spent material. This shows that the process not only recovered the cathode material, but also restored it to a form that could be used again in a LiFePO₄ battery. The high purity of the recovered LiFePO₄ makes direct regeneration possible, which creates a more direct path from spent cathode material back to a functional battery material. This supports the development of more closed-loop approaches to LiFePO₄ battery recycling.Beyond recovering the cathode material, the process could make LiFePO₄ recycling more practical and efficient. Avoiding excessive mechanical pulverization facilitates subsequent magnetic separation, enabling high-purity separation of cathode and anode sheets while minimizing cross-contamination and benefiting subsequent regeneration. Magnetic separation pretreatment lowers the pyrolysis temperature of the cathode sheets to 400 °C, thereby reducing energy consumption. The life-cycle and economic analysis also suggests that the process could work on a larger scale, with lower energy use and greenhouse-gas emissions than the conventional recycling methods evaluated in the study. Recovering both LiFePO₄ and aluminum could also improve the economic value of the process.