Green Li-ion ($35M for lithium battery recycling)

Green Li-ion, a lithium-ion battery recycling technology company founded in 2020 in Singapore, specializes in sustainable energy storage and battery recycling using modular technology to fully recycle Lithium-Ion batteries. They have recently secured $20.5 million in Pre-Series B funding and closed their $11.55 million Series A funding round. The company’s patented technology could be the solution to recycling lithium-ion batteries, speeding up processes, and lowering costs.

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Challenges: lithium battery recycling

The rapid growth of electric vehicles has a significant impact on the demand for Li-ion batteries. By 2030, it is anticipated that 140 million electric vehicles will be on the roads worldwide, while 11 million metric tons of Li-ion batteries will reach the end of their service lives. Currently, most used Li-ion batteries are discharged in landfills, and less than 5% of batteries are recycled.

To prepare spent lithium-ion batteries for recycling, they are typically dismantled, crushed, or shredded into a black mass, which is either melted (pyrometallurgy) or dissolved in acid (hydrometallurgy). There are numerous types of impurities in black mass, particularly those derived collectively from different types of lithium-ion batteries. Failure to remove them effectively impairs the purity of precious metals recovered through recycling.

The current method of simply shredding everything and trying to purify a complex mixture results in expensive processes with low value products. Thus, there is a need for a lithium-ion battery recycling process that can more effectively remove impurities from black mass. There is also a need to remove impurities in a more efficient manner that requires less equipment and reduces the amount of precious metals available for recovery as little as possible.

This book Recycling of Power Lithium-Ion Batteries explores the past, present, and future of power lithium-ion battery recycling, from the governing regulatory framework to predictions of the future of the industry. (see on Amazon)

Green Li-ion Technology

Green Li-ion’s recycling system can remove most impurities from black mass and extract graphite and cathode metal salts at a high purity over 99% that can be used for cathode fabrication. The entire recycling process takes 12 to 14 hours, including processes of sulfuric acid leaching, impurity removing, cathode precipitation, and lithium extraction. The final discharge is a slightly saline solution that is not harmful to the environment.

Leaching metal elements from spent Li-ion batteries

As shown in the above figure, the black mass is poured into the first reactor. In the first phase of leaching, sulfuric acid (H₂SO₄) is added to the black mass in the first reactor to form a leaching solution. To facilitate leaching as a co-digestant, hydrogen peroxide (H₂O₂), 50 ml of hydrogen peroxide (30% concentration) per liter of solution, is added to the first reactor. The contents of the first reactor are agitated by an agitator for one hour.

During the first phase of leaching, the sulfuric acid reacts with iron present in the black mass to produce ferrous iron (Fe²⁺). The hydrogen peroxide converts ferrous iron into ferric iron (Fe³⁺). The ferric iron reacts with the sulfate ions to form iron sulfate (Fe₂(SO₄)₃).

In the second phase, deionized water (H₂O) is added to the first reactor to dilute the sulfuric acid to a concentration of about 2M. The agitator maintains the agitation of the contents of the first reactor for about 30 minutes.

Throughout the first and second phases of leaching, the temperature of the contents of the first reactor is maintained between 70 and 90°C.

After the first and second phases of leaching, the leaching solution from the first reactor is discharged through an outlet valve and pumped into a second reactor through a filter. The undissolved graphite materials are extracted through the filter.

Removing iron(III), aluminum(III), titanium(IV), fluoride, and copper(II) impurities

Sodium hydroxide (NaOH) is added to the leaching solution in the second reactor in order to adjust the pH to between 1.2 and 2.15.

Iron (Fe) powder is added to the leaching solution, about 2.5 g of iron powder per liter of leaching solution, over a period of 15 minutes while maintaining the temperature of the contents of the second reactor at about 60°C. Iron powder will react favorably with copper in the leaching solution, resulting in the copper cementation:

Fe + Cu²⁺ → Fe²⁺ + Cu

A pH of 1.2 or 2.15 results in the cementation of about 90% of copper in the leaching solution, i.e. copper removal. When the pH is adjusted to 3.07, copper cementation in the leaching solution falls below 80% over the same period.

In the second reactor, the sulfuric acid and hydrogen peroxide added during the first phase of leaching in the first reactor are present. During copper cementation, the hydrogen peroxide oxidizes the ferrous iron to ferric iron. The ferric iron reacts with the sulfate ions to produce iron sulfate (Fe₂(SO₄)₃).

Some fluoride (F^–) may be removed during the leaching process in the first reactor, but sufficiently undesirable and toxic amounts will remain as fluoride ions in the leaching solution transferred to the second reactor. Calcium oxide (CaO) is added to the second reactor, about 20-40g of CaO per kg of the black mass previously added into the first reactor. After adding lime, the contents are allowed to rest (with continued agitation) for 30 minutes at 40°C.

To prevent the lime from interfering with the iron powder’s ability to induce copper cementation, lime should not be added until after the iron powder has completely cemented copper from the second reactor’s contents.

After about 30 minutes of rest, more sodium hydroxide is added to the second reactor to adjust the pH of its contents to about 6. The pH transition triggers the precipitation of the other impurities of fluorine, iron, phosphorus, titanium, and aluminum.

From about pH 2.2, fluoride starts to precipitate as calcium fluoride (CaF₂):

CaO + 2HF → CaF₂(s) + H₂O

At pH 3.12, 4.06 and 5.24, the concentration of fluoride is reduced consecutively and significantly.

As the pH of the contents of the second reactor rises to about 3, the sodium hydroxide precipitates iron ions as iron hydroxide. The iron that is not precipitated as iron hydroxide reacts with phosphate ions (PO₄^3-) in the second reactor’s contents to precipitate as iron phosphate (FePO₄). The precipitation begins at pH 3 and increases up to pH 4.5, where essentially all iron and phosphorus in the leaching solution were precipitated.

As the pH of the second reactor’s contents rises above 4, the hydrogen peroxide which was added in the first reactor and transferred in the leaching solution to the second reactor pushes the oxidative states of titanium and aluminum to titanium (V) and aluminum (III), respectively, thereby initiating precipitation of their hydroxides Ti(OH)₄ and Al(OH)₃. The concentration of aluminum, iron and titanium reduced significantly.

Once the pH reaches about 6, the contents of the second reactor are allowed to rest (with continued agitation) for 60 minutes at 60°C. The concentration of aluminum, iron and titanium further reduced significantly at pH 6. After 60 minutes, the second reactor’s contents are released through an outlet valve and filtered to remove copper and precipitates (calcium fluoride, iron phosphate, iron hydroxide, titanium hydroxide, and aluminum hydroxide), thereby removing a significant amount of the impurities that were originally existed in the black mass. Less than 10mg/l of impurities from the black mass remain in the second reactor’s final contents. The total duration of the leaching and impurity removing processes is 3 to 4 hours.

Recycling nickel(II), cobalt(II) and manganese(II)

The filtered and purified solution from the second reactor is introduced into the third reactor to extract cathode metals cobalt, nickel, and manganese by adjusting the pH to 11 with NaOH and a proper amount of NH₃·H₂O. Initial precipitation of nickel(II), cobalt(II) and manganese(II) occurs at pH values close to or even above 6.7. Therefore, nickel(II), cobalt(II) and manganese(II) do not precipitate until all the copper(II), iron(III), titanium(IV), and aluminum(III) has precipitated.

The third reactor’s final contents which contain Ni_xMn_yCo_z(OH)₂ salt precipitation are discharged via a valve and pumped to the fourth reactor via a filter that filters Ni_xMn_yCo_z(OH)₂ salts.

Recycling lithium

In the fourth reactor, the solution was neutralized by subsequently adding stoichiometric amounts of formic acid and saturated sodium carbonate (Na₂CO₃). Li₂CO₃ precipitates out. The fourth reactor’s final contents are discharged through a valve and pumped to a filter that filters Li₂CO₃, and the final slightly saline solution that is environmentally safe is discharged.

The system recovers graphite and cathode metal salts (such as Ni_xMn_yCo_z(OH)₂ and Li₂CO₃) with purity levels exceeding 99%. The technology enables the production of cathodes that are 99.9% pure.

Green Li-ion Products

The company has developed a multi-cathode processor GLMC-1 that recycles spent lithium-ion batteries directly into 99.9% pure cathodes, thereby accelerating current recycling processes by more than 10 times and reducing costs by more than 4 times.

The equipment occupies 80 m². Each machine has the capacity to recycle up to 728 tones per year, or 2 tones per day if operating in 24-hour shifts.

Green Li-ion product (Source Green Li-ion).

Green Li-ion Funding

Green Li-ion has raised a total of $35.5M in funding over 4 rounds, including two Seed rounds, a Series A round, and a Series B round. Their latest funding was raised on Mar 10, 2023 from a Series B round.