Scientists from the Southern University of Science and Technology in Shenzhen jointly with the Hunan University of Technology have developed an innovative method for recycling spent lithium-ion batteries. The new technology makes it possible to recover lithium with a high degree of completeness and nearly halve energy consumption. This is especially relevant in view of projections indicating that the global volume of spent batteries could reach 11 million tons by 2030, while demand for lithium to be used in electric vehicles and electronics will continue to grow exponentially.
In contrast to conventional recycling methods such as hydrometallurgy, the new process does not require the use of corrosive acids and does not generate large volumes of toxic waste. While conventional acid technologies provide high metal recovery, they involve complex separation and purification phases. Electrochemical methods are considered more environmentally friendly, but they have been hampered by low energy efficiency until now. In the later stages of electrolysis, a significant portion of the input energy is spent on secondary processes, such as the release of oxygen, rather than on recovering lithium. The researchers set the goal of maximizing the use of input electrical energy specifically for lithium leaching.
The approach proposed by the Chinese scientists consists in dividing the process into two stages with different operating modes. During the first stage, the cathode material is placed in a sodium chloride solution, after which a voltage is applied for a limited time of about 55–70 minutes. This kicks off the so-called electrochemical double oxidation: lithium ions actively exit the material’s crystal lattice.
A key feature of this method is revealed during the second stage. The researchers stop the voltage completely, leaving the electrode in the solution for several hours. Despite the absence of an external energy source, lithium recovery continues until it reaches almost 100%. Figuratively speaking, the system starts working via internal chemical transformations.
The scientists explored the mechanism of this phenomenon using X-ray diffraction, electron spectroscopy and other structural analysis methods. They found that, during the first stage, voltage not only removes some of the lithium but also converts the so-called lattice oxygen into a more oxidized, energetically active state. This activated oxygen is gradually restored during the second stage, enabling ion exchange: sodium ions from the solution replace the lithium remaining in the structure. As a result, recovery continues without additional energy consumption.
This method was tested on real spent cathodes of various compositions: NCM111, NCM523, NCM622 and NCM811. In all cases, lithium extraction reached some 98%, while nickel, cobalt and manganese essentially did not pass into solution: their losses did not exceed 0.4%. This ensures that the process is highly selective and makes it easier to obtain a pure product. A pilot installation with a loading rate of up to 500 g of material per cycle confirmed the scalability of the technology. The resulting lithium carbonate had a purity of over 99.5%, meeting battery-grade requirements.
Economic calculations showed that the two-stage process reduces energy consumption by about 50% compared to conventional electrochemical recycling. Calculated with reference to a ton of recycled cathodes, energy savings alone amount to some $142, with a potential gross profit of more than $600 per ton.
