The technology overview: closing the lithium supply gap with direct lithium extraction (DLE) and battery recycling
This article is part of our lithium series. Read the main article here. Keen to know more about the market opportunity? See this article.
By Max Werny, Yair Reem, Iris ten Have, and Fernanda Bartels
The status quo — hard rock mining and evaporation ponds
Lithium is primarily won from hard rock (60%) and brines (39%). Lithium-rich ores are processed via acid roasting, an energy-intensive process that involves subjecting the ore to high temperatures (1100 °C) and concentrated acids. Hard rock mining and refining projects usually have shorter project development and processing times compared to brines. Their emissions, however, are high (15 t CO2/t LCE for spodumene versus 5 t CO2/t LCE for brines) and their profit margins lower.
Now onto brines. While a large share of the world’s lithium sits in brines, their utilisation is only starting to gather pace due to the significant surge in lithium demand and increasing costs associated with hard rock mining projects. In comparison to hard rock resources, lithium (Li+) is often less concentrated in brines. Moreover, it is often accompanied by high concentrations of other ions like magnesium (Mg2+), calcium (Ca2+), sodium (Na+), boron (B3+), iron (Fe2+), and potassium (K+). To obtain lithium compounds, such as lithium carbonate (Li2CO3) or lithium hydroxide (LiOH), the unwanted ions need to be selectively removed.
In a traditional brine operation, lithium-rich brine is pumped to the surface and concentrated by evaporation in a series of artificial ponds for 12–18 months. Salts, such as sodium chloride and potassium chloride, are precipitated and removed while concentrating the lithium. The brine is then treated with chemicals (calcium oxide/hydroxide, sodium carbonate) and/or filtered to remove impurities such as magnesium (Mg2+), sulfates and calcium (Ca2+) ions. Finally, the concentrated lithium solution is converted with soda ash (sodium carbonate) to technical-grade lithium carbonate, which, upon further purification, can be used for battery production. In certain cases, lithium is precipitated as lithium phosphate, which has a markedly lower solubility than lithium carbonate. Lithium phosphate is then refined into battery-grade lithium hydroxide via an electrochemical process.
Extracting lithium via solar evaporation and chemical precipitation does have significant drawbacks, however: Evaporation and precipitation are slow and uneconomical, more than 40% of lithium is lost, and the process as a whole usually has a significant environmental footprint.
The game changer — direct lithium extraction (DLE)
The increasing demand for lithium, together with growing environmental awareness, has stimulated researchers, entrepreneurs, corporates and governments to develop technologies that can directly extract lithium from brines without the need for time- and space-consuming evaporation ponds. These are collectively referred to as direct lithium extraction (DLE) technologies. In DLE, lithium is extracted from the brine in a single-stage chemical process in the space of hours or days. The lithium-free eluate is then ideally reinjected, thereby significantly reducing the water consumption of the process.
DLE technologies not only facilitate a faster, more efficient, and cheaper extraction of lithium from more concentrated brines in salars, salt lakes and geothermal operations, but can also process oil and gas brines and groundwater brines. These have lithium concentrations of only several tens to a few hundreds parts per million (ppm) of lithium and are still largely untapped. Five chemical technologies will be at the forefront of the DLE industry in the years to come: adsorption, ion exchange, solvent extraction, membrane separation and electrochemical separation/refining. Below, we will discuss the pros and cons of each DLE technology.
Adsorption
One of the technologically most established routes for DLE from a brine is the physical adsorption of lithium chloride (LiCl) onto a solid sorbent. A stripping solution, usually warm or hot water, is used to desorb the LiCl from the sorbent. Novel approaches involve the use of CO2 to regenerate the sorbent, enabling fast regeneration and lowering the water intensity of the process.
Maturity: Pre-commercial to commercial (TRL 7–9)
Pros:
- Sorbent regeneration/lithium elution is performed with water and not acid, resulting in longer sorbent lifetimes
- Most mature DLE technology
- Simple process design
Cons:
- Relatively low sorbent capacities, resulting in lower LiCl concentrations in the eluate
- Ideally requires temperatures above 40 °C to compensate for the lower lithium capacities of sorbents (higher temperatures lead to faster lithium uptake)
- High water consumption
- Exchange of end-of-life sorbent can cause significant downtime
- Often requires an additional concentration step after the extraction
Ion exchange
A second pathway for DLE that is relatively mature used ion exchange technology. Here, lithium ions (Li+) from a brine are chemically bound by a solid ion-exchange sorbent. The sorbent acts like a sieve for lithium due its well defined porosity, resulting in a selective uptake of lithium ions. The lithium ions are then exchanged with other positively charged ions from a stripping solution (e.g. H+ from hydrochloric acid, HCl). Common ion-exchange sorbents include lithium titanium oxides, lithium manganese oxides and lithium aluminium-layered double hydroxide chlorides.
Maturity: Pre-commercial to commercial (TRL 7–9)
Pros:
- High sorbent capacities, facilitating high LiCl concentrations in the eluate
- High selectivity for lithium leading to high purity levels and minimal contamination from e.g. sodium (Na+) or potassium (K+) in the strip solution
- High lithium concentration in the strip solution
- Simple process design
Cons:
- Large amounts of acid/base required, which can result in high OPEX and CAPEX, especially if a production plant for acids and bases is required on site
- Sorbent degradation possible due to repeated exposure to acid
- Exchange of end-of-life sorbent can cause significant downtime
- May require an additional concentration step after the extraction
- Sorbent costs can be high
Solvent extraction
The third pathway uses a solvent to extract lithium instead of a solid sorbent. Lithium ions (Li+) or lithium chloride (LiCl) is extracted from a brine into an organic solution, typically containing kerosene and an extractant, such as tributyl phosphate, trioctylphosphine oxide or beta-diketone compounds.
Maturity: Pre-commercial (TRL 7–8)
Pros:
- High concentration of lithium (chloride) in the stripping solution — no additional concentration step required in comparison to adsorption and ion exchange
- Continuous process (high throughput)
- Can have a high selectivity for lithium (Li+) versus sodium (Na+) and magnesium (Mg2+)
Cons:
- More expensive than other technologies due to high OPEX and CAPEX
- Brine may require post-treatment after DLE step due to solvent residues
- Use of organic solvents (environmental risks, health risks, fire risk with high temperature brines, etc.)
- Corrosion of equipment
(Electro-)membrane separation
The fourth DLE process uses a lithium-selective membrane to extract lithium from brines. Specific sub-categories include nanofiltration, reverse osmosis or electrodialysis. In most cases, membranes are used for upstream pre-concentration or post-DLE purification. Novel electrodialysis technologies are now also targeting the DLE process step.
Maturity: Lab to pre-commercial (TRL 4–8)
Pros:
- High lithium selectivities
- High lithium concentrations in the eluate
- Novel electrodialysis technologies have low energy requirements
- No chemicals used
- Can be continuous (high throughput)
Cons:
- In certain cases limited to brines with low magnesium (Mg2+), calcium (Ca2+), sodium (Na+) or potassium (K+) concentrations due to membrane fouling/scaling — pre-treatment may be required
- Can be energy-intensive
- Often water-intensive
- Membranes can be expensive
- In certain cases not suitable for directly treating high temperature brines (e.g. geothermal brines)
Electrochemical separation or refining
The fifth and last DLE technology uses electrochemical principles to extract lithium. For example, reversible electrochemical reactions at electrodes (intercalation chemistry, like in a lithium-ion battery) or electrolysis. The latter is usually employed for lithium refining (i.e. purification) and/or downstream processing of lithium compounds.
Maturity: Lab to pre-commercial (TRL 4–8)
Pros:
- Novel processes have a low energy and water consumption
- High selectivities
- No chemicals used
Cons:
- Fouling can be an issue
- Membranes can be expensive
- Long-term stability of electrodes has not been fully evaluated yet for brines
Who are the main players?
Various technology providers and mining companies are working hard behind the scenes to bring DLE technologies to market. A majority of these companies are specialised in adsorption and ion exchange sorbent technologies, which, at this point in time, are starting to approach full technological maturity. While companies such as Livent and Sunresin have already established their respective sorbent technologies at commercial or pre-commercial scales, several promising technologies, such as electrochemical cells and more energy-efficient electrodialysis technologies, are still under development.
Closing the loop — Battery recycling
Apart from extracting more lithium through optimised mining and refining processes, we also need to utilise the resources that we already have. Recycling represents an attractive pathway to extract lithium and other valuable materials (graphite, cobalt, nickel, manganese) from end-of-life lithium-ion batteries and manufacturing scrap. It is particularly relevant for countries and geographies with a lack of resources or established extraction projects (e.g. Europe). From an environmental point of view, battery recycling saves huge amounts of CO2. Recycled raw materials, won from a combination of mechanical recycling and hydrometallurgy, have a footprint of only 8 kg CO2e/kWh, which is 72% less than that of virgin raw materials (29 kg CO2e/kWh).
Current state-of-the-art battery recycling processes are complex and typically involve a series of processing steps: After collection, the battery packs are tested, discharged and disassembled. The battery modules or cells are then crushed by dry or wet shredding (in certain cases under inert gas), impact milling or shockwaves. Following this mechanical treatment, the resulting black mass is separated into different material fractions via sieving, froth flotation, density or magnetic separation. To obtain black mass with higher purities, the disassembled modules or cells may also undergo pyrolysis or atmospheric thermal processing before or after shredding.
This removes impurities (plastic, binder, electrolyte), optimises the separation of electrode active material and current collector foil, and changes the phases of metal components to a more processable, reduced form for further processing. The procedures also help to deactivate the batteries. Finally, the isolated black mass is processed via pyrometallurgy, hydrometallurgy or direct recycling. While pyrometallurgical and hydrometallurgical processes only enable the recovery of metal salts, direct recycling yields high value cathode materials that can be directly fed into lithium-ion battery production after regeneration. Recycled raw materials from direct recycling are expected to have significantly reduced footprints (e.g. 1.7 kg CO2e/kWh for a LiCoO2 cathode material with an energy density of 0.3 kWh/kg).
Similar to the previous section on direct lithium extraction (DLE) technologies, we will discuss the individual recycling technologies as well their strengths and weaknesses below. Several companies operating in the battery recycling space outsource some of their processing steps (e.g. mechanical recycling or hydrometallurgy) to other recycling companies.
Pyrometallurgy (Smelting)
The most mature battery recycling technology, pyrometallurgy, involves the thermal treatment of whole or shredded lithium-ion batteries at temperatures up to 1500°C to form an alloy containing cobalt (Co), nickel (Ni), and copper (Cu). Lithium (Li), aluminium (Al), manganese (Mn) and silicon (Si) are separated as a slag. Both the alloy and the slag need to be refined by means of hydrometallurgy to recover the individual metals. Due to the technological complexity of refining the slag, it is often used in the construction industry or disposed of in landfills.
Maturity: Commercial (TRL 9)
Pros:
- Established, robust process
- High-throughput processing
- High input flexibility
- High recovery rates for nickel and cobalt
Cons:
- High CO2 footprint
- Energy-intensive process (high OPEX)
- No graphite recovery
- Limited lithium recovery (slag is often disposed of or used in construction)
- No electrolyte recovery
- Fouling in the oven possible due to thermal at high temperatures
- High emissions (SOx, NOx, HF, HCl, etc.) require gas cleaning systems
Hydrometallurgy
The second mature technology, hydrometallurgy, describes the chemical process of treating black mass or lithium-ion batteries with acid to leach the metals into solution. The dissolved metals are then precipitated sequentially and isolated as battery-grade salts, often in the form of sulphates. Alternatively, the metals can also be recovered by means of solvent extraction or selective adsorption.
Maturity: Pre-commercial to commercial (TRL 7–9)
Pros:
- High recovery rates for all metals and graphite
- High technological maturity
Cons:
- High CO2 footprint (slightly lower than pyrometallurgy)
- Energy-intensive process
- Involves the use of large amounts of chemicals
- High OPEX
- Can have a high CAPEX
- High water consumption
- No electrolyte recovery
- Time-intensive
- High amounts of metal sulphates produced as byproducts
Direct recycling
The third recycling method, direct recycling, involves the recovery, regeneration, and reuse of battery components without breaking down their chemical structure. The term is most commonly used to describe the thermal annealing of cathode active materials (CAMs) with lithium-containing compounds (cathode healing/re-lithiation) after their separation from black mass. Novel processes use plasma for the sorting, purification, and repair of cathode materials.
Maturity: Lab to pre-commercial (TRL 4–7)
Pros:
- Low energy input
- Low OPEX
- Low CO2 footprint
- High recovery rates, even for lithium, graphite and electrolytes
- Minimal waste (circular)
Cons:
- Chemical re-lithiation treatment has to be adapted to the cathode composition
- Cathode materials have to be physically separated from black mass and, in certain cases, from each other
- Nascent technology that is unproven at scale
Electrochemical
Electrochemical processes are complementary to hydrometallurgical approaches. An electrical current is either applied to regulate the flow of dissolved metal ions from a leaching solution through a conductive membrane (electro-filtration) or to deposit the ions as solid metal on a substrate (electroplating or electro-extraction).
Maturity: Prototype to pre-commercial (TRL 6–8)
Pros:
- Low carbon footprint
- Low energy input (low OPEX)
- High recovery rates for all components (potentially also including the electrolyte)
- Minimal waste generation
Cons:
- Requires hydrometallurgy to bring cathode active material into solution
- Nascent technology
Who are the main players?
Hydrometallurgy is gaining a huge amount of traction in the world of battery recycling due to its superior performance versus pyrometallurgy. Several large corporates in the US and Europe already use hydrometallurgy at (pre-)commercial scales. That being said, most hydrometallurgy processes are not perfect and in need of further optimisation. The less mature route of direct recycling is currently only being pursued by a handful of companies but will presumably become more widely adopted in the near future, given its potentially higher recycling efficiencies, lower environmental footprint, energy efficiency and compatibility with disassembly and demanufacturing approaches.
Powering the future with sustainable lithium supply chains
The critical role of lithium in decarbonising transport and energy storage is undeniable. As we conclude this exploration of direct lithium extraction (DLE) and advanced battery recycling methods, it is clear that both technologies are strategically important for building more sustainable and resilient lithium supply chains. While DLE offers an environmentally friendly and efficient way to extract lithium from low concentration resources, many of which are currently untapped, battery recycling presents a circular solution to recover not only lithium, but a number of other valuable materials, such as graphite and cobalt. By prioritising DLE and battery recycling, we can significantly reduce the environmental impact of the lithium industry while also greatly increasing its output and resilience.
Are you an entrepreneur pushing the frontiers of DLE and/or battery recycling technologies? Or an investor or expert in these sectors? Reach out to our team — we would love to connect.
