Northvolt ($7B for producing the greenest lithium battery)

Northvolt manufactures the world’s greenest lithium-ion batteries by managing the supply chain to reduce the transport distance of raw materials, using hydroelectricity to power the gigawatt factory, and making batteries from spent batteries.

Challenges: lithium battery

As road transportation is responsible for approximately 16% of human-made carbon dioxide (CO₂) emissions, electric vehicles could significantly lessen this environmental burden. Rapid expansion of electric vehicles increases demand for lithium-ion batteries. The global production of lithium-ion batteries was around 154 GW h in 2017 and could exceed 2,000 GW h by 2028. However, the production and disposal of lithium-ion batteries today are not at all environmentally friendly.

The mining and refining of essential battery materials produces sulfur dioxide and nitrogen oxides, which contribute to environmental issues such as acid rain and smog. Transporting of raw materials and energy-intensive manufacturing processes cause copious carbon dioxide emissions. In addition, 95% of spent batteries today end up in landfills, which poses a risk of toxic chemical leaching.

Northvolt Technology

Northvolt could manufacture lithium-ion batteries that emit 60-70% less carbon dioxide than comparable batteries. Northvolt accomplishes this in three ways: (1) by locating its mining and refining operations nearby; (2) by utilizing hydroelectricity to power its factory; and (3) by recycling used batteries to create new ones.

Refine raw materials close to where they are mined

The mining, refining, and transportation of the cathode materials, such as lithium, nickel, manganese, and cobalt, are reportedly responsible for 30% of the battery’s greenhouse gas emissions. Therefore, the manner in which these raw materials are supplied to battery manufacturers is crucial in determining the eco-friendliness of their batteries.

Northvolt short supply chain to reduce carbon dioxide emission. — Northvolt reduces carbon dioxide emission with short supply chain.

Northvolt deals directly with mining companies and refiners. For example, Northvolt’s lithium is derived from spodumene ore mined in Australia and Canada and refined into lithium hydroxide at plants located near these mines. Northvolt can avoid transporting the vast majority of the ore’s mass by locating the mining and refining operations nearby.

Hydroelectricity powers gigawatt factory to make batteries

Northvolt’s batteries use the most recent generation of cathode material, with an 8:1:1 ratio of nickel to manganese to cobalt (NMC) to keep the high energy density but maintain the stability and cycle life. NMC batteries power Nissan Leaf, Chevy Volt, and BMW i3 and their demand is growing.

However, the production of NMC 811 batteries is difficult, partly because the cathode’s reactive nickel ions are extremely sensitive to moisture. These cathodes with a high nickel content are considerably more difficult to manipulate because they have to be mixed and coated in extremely dry conditions. Factories are required to operate a portion of their production lines in large, climate-controlled dry rooms, which increases the total energy consumption of the process.

Northvolt factory powered by hydroelectricity — Northvolt uses hydroelectricity to power gigawatt factory.

All the steps involved in transforming ore and other raw materials into typical NMC-based Li-ion batteries emit approximately 42 kg of carbon dioxide per 1 kW h of capacity, with approximately 40% of those emissions occurring during cell manufacturing. The Northvolt gigawatt factory, powered by hydroelectricity, should avoid almost all of that carbon dioxide.

Manufacture batteries from used batteries

Northvolt has developed its own hydrometallurgical method for recycling used batteries to make new ones. The hydrometallurgical process uses significantly less energy than pyrometallurgy, and many of the recycling reagents can be reused. Utilizing hydroelectricity to power the process will further improve the sustainability of Northvolt’s recycling procedure.

1. Solution discharge of cells and modules for battery recycling

The batteries are crushed prior to the hydrometallurgy process. Discharging the batteries is crucial for safety reasons because spent batteries have “voltage rebound.” Voltage rebound can occur minutes to hours after a battery is discharged to 0 V, and the voltage of the battery can rise to 2.5 V or higher. This is extremely dangerous when the cell is being crushed, as the anode and cathode materials could come into contact, resulting in a short circuit or self-ignition. For safe crushing, a deep discharge to a voltage between 0.5 V and 0 V is required.

Northvolt develops a solution discharge process for the deep discharging of used lithium-ion batteries that allows for the safe, fast, low-cost, and effective discharging of batteries to a low voltage of about 0 V and, at the same time, allows for the effective prevention of the voltage rebound to greater than about 0.5 V. The solution discharging process includes the following steps:

Step 1. Voltage pre-check

Before solution discharging, voltage pre-check of used batteries is typically performed to detect damaged batteries. Damaged batteries can result in the formation of gas in the battery, which can increase the internal pressure and cause an explosion and/or a fire.

If the check reveals that the voltage is irregular, such as fluctuating instead of remaining constant, or if it is outside the normal voltage range, a vent of the battery is opened to release internal pressure and to reduce the risk of self-ignition or fire during discharging.

Step 2. Initial discharging of batteries (optional)

Northvolt initial discharging of batteries — Initial discharging of batteries.

If spent batteries have a high voltage of 3.8 V at state of charge (SOC) of 30% or higher, it is preferable to perform an initial discharging in a low conductive discharge aqueous solution (10% of sodium carbonate, 60 ºC, pH 11 to 12) in order to initially discharge the batteries to a lower potential. The batteries are discharged slowly to avoid a destructive release of energy.

The spent batteries are placed in a holder and immersed for five hours in the conductive discharge solution. The solution’s pH and temperature should be considered. The preferable pH range is 11 to 12. If the pH falls below this range, battery casing metal may corrode. If the pH is above this range, plastics, in particular the gaskets separating the terminals, may break down, increasing the risk of a short circuit and thermal runaway.

Batteries can be safely discharged at temperatures between 60 and 80 ºC. If the temperature of the discharge medium is set above this range, thermal runaway is more likely to occur. If the temperature of the discharge medium is below this range, the discharge process will be slowed.

At the end of the time, the batteries are removed from the solution and rinsed. The solution is subjected to recovery. The voltage of all batteries can be reduced to approximately 2.3 V (0% SOC).

Step 3. Deep discharging of batteries

Northvolt deep discharging of batteries — Deep discharging of batteries.

To perform deep charging of batteries, the (initially discharged) batteries in the holder are immersed in 60 ºC discharging solution (10% of sodium carbonate). The positive and negative terminals of the batteries are covered with highly conductive bulk materials, such as stainless steel beads, causing a short circuit. The stainless steel beads have a uniform diameter of 0.5 to 1 mm, allowing for a good contact with the electric poles and formation of a uniform conductive path between the poles.

At the end of the time, the batteries were removed and rinsed. The stainless steel beads are separated from the solution by a magnet. The solution is subjected to recovery. After 24 hours, the voltage of the batteries remains constant and between 0.1 and 0.5 V, making the subsequent crushing process safe.

2. Create cathode materials directly from recycling batteries

After crushing of used batteries, separation and sieving processes produce black mass for the subsequent hydrometallurgical process to recycle cathode materials. Similar to Ascend Elements, Northvolt synthesized cathode material directly from the hydrometallurgy process using a simple method involving uniform-phase precipitation as the starting material. The method is more efficient, environmentally friendly, and economical than conventional Li-battery recycling technologies, such as Lithion Recycling, Li-Cycle, and Green Li-ion, which separate Ni, Mn, and Co during the hydrometallurgy process and then recombine them to create cathode materials.

The process is detailed in the following schematic flowchart:

Northvolt battery made from battery — Northvolt synthesized cathode material directly from the hydrometallurgy process.

The process comprises the following steps:

Step 1. Prepare a leachate from black mass

By adding sulfuric acid (H₂SO₄) as the leach agent and hydrogen peroxide (H₂O₂) as a reducing agent, black mass rich in cathode active materials of Ni, Co, and Mn is leached. The pH of the leach solution is below 1.5. Metallic elements in the black mass are dissolved in the leach solution during leaching. Filtration of leaching residues such as graphite, plastic species, and undissolved particles.

Step 2. Removing impurities

The leachate contains unwanted ions such as Cu, Fe, Al, and Zn. Prior to impurity removal, the concentration of each ion in the leachate is determined, as the solubility of these ionic compounds, which is a function of the pH of the solution, is affected by the concentration. A total concentration of the ions in the leachate can then be calculated. Therefore, it is possible to calculate the solubility of each active meal of Ni, Co, and Mn at a specific pH of the leach solution.

To remove ion impurities, the pH of the leachate is first raised to between 1 and 1.4 with the addition of Ni, Co, and Mn hydroxide (NCM hydroxide). NCM hydroxide is preferred to prevent the introduction of additional ion impurities. Cu is extracted via solvent extraction using LIX® diluted kerosene. Then, the pH of the leachate is further raised to 3-5 by adding NCM hydroxide in order to precipitate Al, Fe and any remaining Cu and Zn. The precipitates are removed through filtration. Traces of Fe, Al, Zn, and Cu can be removed from the leachate by ion exchange. Then, the leach solution mainly contains active metals of Ni, Co, and Mn, as well as highly soluble impurities such as Li, Na, and trace amounts of Mg and Ca.

Step 3. Adjusting the concentration of the active materials

The concentration of each ion, including active metal ions and ionic impurities, is then determined. The solubility of each active metal Ni, Co, and Mn in the leachate at a particular pH is calculated, which enables adjusting the concentration of each active metal ion to ensure precipitation of the precursor at the desired target ratio of the active metals. Based on the total concentration of ions, the concentrations of Ni, Co, and Mn are adjusted to a desired level by adding respective nickel sulfate (NiSO₄), cobalt sulfate (CoSO₄), and/or manganese sulfate (MnSO₄).

Step 4. Coprecipitation of NMC hydroxide (Ni_xMn_yCo_z(OH)₂)

After adjusting the concentration of each active material to the desired level, the pH of the leachate is raised to between 8 and 9 by the addition of NaOH, resulting in coprecipitation of the active materials as hydroxide in a ratio corresponding to the desired active material target ratio while avoiding coprecipitation of ionic impurities such as Li, P, Mg, Na, Ca, and Si. The coprecipitated NMC hydroxide precursors are filtered, washed, and used for subsequent fabrication of cathode materials.

The leachate remaining (mother liquor) after coprecipitation, which contains unprecipitated active metals, is subjected to subsequent recovery treatment to save resources and enhance sustainability. The lithium is recovered from the leach solution by precipitating lithium carbonate with sodium carbonate. The sodium sulfate-containing solution is transferred to a crystallization unit, where sodium sulfate crystals are produced via evaporation crystallization and separated.

Northvolt Products

Most Northvolt batteries are destined to power electric vehicles. Northvolt products include cylindrical cells, prismatic cells, and energy storage systems. In March 2021, Northvolt acquired Cuberg, a US startup developing a high performance lithium-magnesium metal battery.