Part 2: Lithium Recovery: A Key Innovation Area in Mining

Last month, we published the first installment of this 2-part series wherein we discussed lithium recovery and different methods of direct lithium extraction.

Circular Lithium Economy

Lithium extraction methods are not yet environmentally sustainable, and even with advances in mining technologies, though plentiful, lithium sources are not endless. To meet demand, technologies and programs that recover and reuse the lithium already in circulation are needed. About 95% of lithium-ion batteries can be recycled into new batteries, and it is estimated that by 2030, there will be 11 million metric tons of spent lithium-ion batteries [10]. Presently, there are two main methods for lithium recovery: pyrometallurgy-based smelting and hydrometallurgy-based leaching. Emerging methods include mechanochemistry separation, recovery from production wastewater, and novel recycling strategies.

Pyrometallurgy-based smelting

Pyrometallurgy involves high-temperature smelting that results in a molten slag mixture of battery components. Cobalt and nickel can be readily separated from the slag, but lithium requires additional processing to extract. Extracting lithium from the slag requires significant energy input that is often not profitable for businesses to pursue [11].

Hydrometallurgy-based leaching

Hydrometallurgy-based leaching processes address some of the concerns about pyrometallurgy-based smelting. Hydrometallurgy-based leaching involves dissolving metals in acid, base, or salt and then purifying the metals using precipitation, ion exchange, liquid-solid or liquid-liquid reactions, or solvent extraction.  Lithium and other materials are recovered through crystallization, electrochemical reduction, or other chemical processes [12]. Hydrometallurgy is much more efficient, with greater metal recovery, but produces large amounts of hazardous waste.

Mechanochemistry separation

Because of the issues with current recovery methods, new technologies are being developed for separating and purifying metals from spent lithium-ion batteries. One group recently reported a process for recovering lithium from cathodes with a variety of chemistries. Their process is based on mechanochemical properties with a series of steps that aid in the purification of lithium without the need for acid solvent, avoiding the production of hazardous waste. Their mechanochemically-induced process involves four steps: 1) ball milling to reduce materials, 2) carbonatization by added water and heating, 3) dissolution in water, filtration, and precipitation of other elements and insoluble byproducts, and 4) evaporation that renders purified Li2CO3 [12].

Wastewater recovery

Brine mining generates a large amount of wastewater that contains additional lithium that is not recovered, and when discharged, it is detrimental to the environment. Several groups have reported novel adsorptive materials that can be used to recover lithium from wastewater, such as magnetic lithium ion-imprinted polymers [13], manganese series adsorbents [14], and metal-organic frameworks paired with adsorbent polyspiropyran (MOF-PSPs) [15].

Desalination and Salt Lake brines could be an eco friendly eco friendly source for Lithium. However, the widespread use of this source is hindered until developing a process with high selectivity for Lithium ions.

Researchers have been focusing on using Nanofiltration membranes for rejecting divalent ions including Magnesium, before conducting the Lithium recovery process [A1]. Rejecting Magnesium ions will enhance the Lithium recovery process by reducing the impact of competing ions. The performance of the Nanofiltration process can be optimized using our Benchtop lab-scale setup.

Recently, more research efforts have been focused on fabricating a novel single ion selective membrane [A2]. Single ion selective membranes can be tailored for high Lithium. At a low technology readiness level, the membrane rejection rate is usually tested and optimized using a very small-scale dead-end stirred cell.

Direct recycling

Compared to traditional “open loop” recycling, where raw material is recovered for use in any number of products, “closed loop” recycling involves directly recycling materials from spent batteries to generate new batteries [16]. In an ideal system, closed loop or direct recycling would involve removing the anode and cathode from a spent battery and reconditioning them for use in a new battery. Though direct recycling in this manner is ideal, it is also labor intensive, requires uniformity in battery design that does not yet exist, and reconditioning the cathode with current techniques does not restore its capacity to 100%. However, researchers have recently reported techniques to fully restore cathode capacity [17]. The ReLieVe (Recycling of Li-ion Batteries for Electric Vehicles) project is an EU endeavor to create a closed-loop recycling infrastructure where all components of the original battery can be reused to produce new lithium-ion batteries.

Summary

Lithium is necessary to fuel the widespread adoption of clean vehicles and support energy storage for green energy sources. However, lithium availability does not come close to meeting demand. Current mining strategies are not easily scalable and are environmentally costly. Identifying more efficient methods for obtaining lithium is essential, and there are many promising technologies for reducing the environmental impact of brine mining and making it more efficient. Additionally, lithium recovery technologies and recycling strategies make use of lithium already extracted. Today, EV lithium-ion batteries have a lifespan of 8-10 years [18]. Developing means to lengthen this timeframe or creating batteries that utilize fewer raw materials would reduce demand for essential battery components like lithium, cobalt, and nickel.


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