Recycling Cathode Materials for Lithium-Ion Batteries

In this paper, a physical recycling method, grinding flotation, is proposed for the separation and recovery of LiCoO2 and graphite from spent LIBs. According to the exploratory experiments, if the mixed electrode materials is ground in the hard grove machine for 5 min before reverse flotation, the concentrate grade of LiCoO2 sinks and graphite floats can reach 97.13% and 73.56%, respectively. Moreover, with the help of advanced analytical technologies, the surface morphology, elemental chemical states and element distribution on the very surface of electrode particles before and after grinding were systematically analyzed to reveal the mechanism of dry surface modification.

Results indicate that the mechanical grinding destroys the lamellar structure of graphite, exposing massive newborn hydrophobic surfaces. Meanwhile, the abrasion of organic film coating the LiCoO2 particles causes its original hydrophilic surface partially regained. Hence, the great wettability difference between LiCoO2 and graphite contributes to an excellent flotation separation. This grinding flotation method is a promising separation method without any toxic emissions or introducing other impurities in industrial application.

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LiBs pose a very specific threat, given that they contain a high percentage of dangerous heavy metals. The recovery of major spent cell components is beneficial both in terms of environmental protection and also for the provision of raw materials. The authors of this article carried out a state of the art on the technologies used in the recycling and regeneration of industrial lithium-ion batteries. The discussion of this research clearly reflects that:

• There are very few studies on the recovery of metals such as graphite, the electrolyte in spent LIBs, and it is our belief that more research is needed in this area.

• The research into the application of microorganisms in the used lithium batteries is few and far between.

• It is important to find ways to recover the precious metals and to recover other materials which may harm the environment, in order to dispose of them appropriately.

A novel process of lithium recovery as lithium ion sieve from the effluent obtained in the process of spent lithium-ion batteries recycling is developed. Through a two-stage precipitation process using Na2CO3 and Na3PO4 as precipitants, lithium is recovered as raw Li2CO3 and pure Li3PO4, respectively. Under the best reaction condition (both the amounts of Na2CO3 and Li3PO4vs. the theoretical ones are about ratio of 1.1), the corresponding recovery rates of lithium (calculated based on the concentration of the previous stage) are 74.72% and 92.21%, respectively. The raw Li2CO3 containing the impurity of Na2CO3 is used to prepare LiMn2O4 as lithium ion sieve, and the tolerant level of sodium on its property is studied through batch tests of adsorption capacity and corrosion resistance. When the weight percentage of Na2CO3 in raw Li2CO3 is controlled less than 10%, the Mn corrosion percentage of LiMn2O4 decreases to 21.07%, and the adsorption capacity can still keep at 40.08 mg g−1. The results reveal that the conventional separation sodium from lithium may be avoided through the application of the raw Li2CO3 in the field of lithium ion sieve.

The hydrometallurgical extraction of metals from spent lithium-ion batteries (LIBs) was investigated. LIBs were first dismantled and a fraction rich in the active material was obtained by physical separation, containing 95% of the initial electrode, 2% of the initial steel and 22% of plastic materials. Several reducers were tested to improve metals dissolution in the leaching step using sulphuric acid. Sodium metabisulphite led to the best results and was studied in more detail. The best concentration of Na2S2O5 was 0.1 M. The metals dissolution increased with acid concentration, however, concentrations higher than 1.25 M are unnecessary. Best results were reached using a stirring speed of 400 min−1. The metals leaching efficiency from the active material (Li, Mn, Ni, Co) increased with the temperature and was above 80% for temperatures higher than 60 °C. The dissolution of metals also rose with the increase in the liquid/solid ratio (L/S), however, extractions above 85% can be reached at L/S as lower as 4.5 L/kg, which is favourable for further purification and recovery operations. About 90% of metals extraction can be achieved after only 0.5 h of leaching. Sodium metabisulphite can be an alternative reducer to increase the leaching of Li, Mn, Co, and Ni from spent LIBs.

The recycling approach uses thermal decomposition of the polyvinylidene fluoride binder to lessen the cohesion of coated active material particles and weaken the adhesion between coating and foil. Then, an air-jet-separator is able to detach the coating powder from the current collector foils while stressing remaining particulate agglomerates. This separation process named ANVIIL (Adhesion Neutralization via Incineration and Impact Liberation) was tested on a laboratory scale with electrode rejects. This was compared to the widely used mechanical recycling process that utilizes a cutting mill to separate the current collector and coating. Intermediates and products were characterized using thermogravimetric analysis, tape adhesion tests, atomic absorption spectroscopy, particle size analysis, and gravimetric sieve analysis. It is found that 97.1% w/w of the electrode coating can be regained with aluminum impurities of only 0.1% w/w, 30 times purer than the comparative process. This demonstrates a more effective recycling process than is currently available that also enables the recapture of lithium from the electrode coating.