Smart mobility - creating a circular economy for automotive lithium-ion batteries

Michal Sura

One of the main objectives of smart mobility is reducing greenhouse gas emissions from the transport sector to slow global warming. In 2017, road transport contributed 21% of the EU's total emissions of carbon dioxide (CO2), the main greenhouse gas (1). In order to reduce greenhouse gas emissions, it is necessary to gradually replace fossil-fuel-powered vehicles by zero-emission vehicles. Battery electric vehicles produce zero direct emissions, and they are very suitable candidates in the effort to achieve carbon neutrality by 2050. Battery electric vehicles use electricity stored in a lithium-ion battery pack to power an electric motor and turn the wheels. Lithium-ion batteries are the most common type of battery used in such vehicles. But in the next few years the large number of lithium-ion batteries will reach the end of their life, and it is obvious that their recycling will become very important for environmental sustainability. The valuable materials within can be recovered, recycled and reused for producing new batteries. The hazardous chemicals and substances from these batteries should be disposed of in a safe and legal manner.

Lithium-ion batteries are currently one of the most suitable energy storage for powering electric vehicles (EVs) with their attractive properties like high energy efficiency, long cycle life, high power density and high energy density. The number of EVs worldwide reached 10.9 million in 2020 (2). It is expected that there will be 115 million EVs globally by 2030 (3). Global demand for lithium-ion batteries is predicted to increase from around 230 GWh in 2020 to 1700 GWh in 2030 (4). In contrast, as of the end of 2019, the number of fuel cell electric vehicles (FCEV) reached 25210. As can be seen, electro-mobility based on lithium-ion batteries is currently the best way to reduce transport's carbon-related emissions. However, modern lithium-ion batteries still have some performance limits (limited lifespan measured in charge/discharge cycles, service life, etc.) and technical barriers (high cost, safety, reliability, etc.). Researchers around the world are working on improving lithium-ion batteries. It is necessary to look for alternatives to electrode scarce materials (cobalt, nickel, etc.) to increase energy density and find materials that reduce environmental impact too. Although lithium-ion battery costs are decreasing rapidly, it is necessary to develop more efficient manufacturing to decrease their cost. It is clear that only enhanced technological innovations will ensure the sustainability and commercial viability of lithium-ion battery systems.

Lithium-ion battery description and working principle

A lithium-ion battery consists of two electrodes (anode and cathode), separated by a porous non-conductive membrane called a separator which is submerged in a non-aqueous liquid electrolyte. The electrolyte is an ionically conductive medium which allows lithium ions to move between the anode and the cathode. The anode and cathode are separated by the separator which allows lithium ions to move through it, but not any electrons, in order to prevent a short circuit. The positive electrode of a Li-ion battery – the cathode is usually made of metal oxides, metal chalcogenides or polyanion compounds, which can store guest lithium ions.

The negative electrode of a Li-ion battery – anode is usually made of graphite or silicon-carbon composites. The typical liquid electrolyte for Li-ion batteries consists of LiPF6 in a mixture of ethylene carbonate (EC) and at least one linear carbonate selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and many additives. The separator for Li-ion batteries is usually a polyolefin membrane. The anodic current collector is usually made of copper and the cathodic current collector is made of aluminum.

Discharging:

During the first stage of discharge, lithium atoms oxidize by forming Li+ ions and electrons, whereas de-intercalated Li+ ions move from the anode to the positive cathode through the electrolyte and the separator. The electrons flow through an external wire from the negative anode to the positive cathode, providing electricity in rechargeable batteries that power an electric motor. At the cathode the electrons recombine with the Li+ ions and are stored in the molecular structure of the active material.

Charging:

As the battery is charged, an oxidation reaction occurs at the cathode. The lithium atoms leave the metal structure and ionize into Li+ ions, and there are lost some negative-charged electrons. Li+ ions move from the positive cathode to the negative anode through the electrolyte and the separator. At the surface of the graphite particles, the Li+ ions and electrons recombine with each other forming neutral lithium atoms and are reintercalated into the molecular structure of the graphite particles.

The most commonly used lithium-ion battery cathode materials

Lithium Cobalt Oxide(LiCoO2) - LCO  

 LCO batteries have very high energy density and a relatively easy manufacturing process. The main disadvantage of LCO are relatively short life span, low thermal stability, low specific power and high cost (because the high cost of cobalt). LCO batteries are widely used in consumer electronics like mobile phones, laptops.

Cycle life: 500 - 1000

Specific energy: 150 - 240 Wh/kg

Lithium Manganese Oxide (LiMn2O4) - LMO

LMO batteries have high temperature stability and safety relative to other Li-ion types. The main advantages are high rate capability due to low internal cell resistance which benefits fast charging and high current discharging. The main disadvantages are lower capacity relative to cobalt-based cathodes and relatively short life span. LMO batteries are usually used in medical devices, power tools, electric bikes.

Cycle life: 300 - 700

Specific energy: 100 - 150 Wh/kg

Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) - NMC

NMC batteries have long life cycle and very high energy density. There is possible to reduce the expensive cobalt content with some compromise in performance. A successful combination is NCM532 with 5 parts nickel, 3 parts cobalt and 2 parts manganese. Other combinations are NMC622 and NMC811. The main disadvantages are slightly lower voltage than cobalt systems and higher cost. Adding a silicon to graphite anode makes it to grow and shrink through charging and discharging, leading to mechanical instability of the cell. LMC batteries are widely used in electric vehicles and energy storage systems (ESS) that need frequent cycling

Cycle life: 1000 - 2000

Specific energy: 150 - 220 Wh/kg

Lithium Iron Phosphate (LiFePO4) - LFP

LFP batteries have very long life cycle, durability, excellent safety and low cost. The main disadvantage are lower nominal voltage which reduces the specific energy and higher self discharge than other types lithium-ion batteries which can cause balancing issues with aging. The cleanliness in manufacturing process is very important for longevity.

LFP batteries are used in electric buses or trucks, where volume or weight is not a problem. 

Cycle life: 2500 - 5000

Specific energy: 80 -120 Wh/kg

Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2) - NCA

NCA batteries have very high specific energy, good specific power and an average life span. The main disadvantages are less safety than other Li-ion battery types (they require extra safety features and circuits for use in electric cars) and relatively short life span. NCA batteries cost more in comparison to other Li-ion battery types. They are used in different applications like electric cars, power grid applications, etc.. Tesla deploys NCA batteries in their electric vehicles.

Cycle life: 500 - 700

Specific energy: 200 - 260 Wh/kg

Lithium Titanate (Li2TiO3) - LTO

LTO batteries have excellent low temperature discharge characteristics, very long life cycle, excellent safety, fast charge capability. The main disadvantages are low density and high cost.

They are used in UPS, military a aerospace applications.

Cycle life: 3,000–7,000

Specific energy: 50 - 80 Wh/kg

Lithium-ion battery value chain

The lithium-ion battery value chain can be divided into six key segments, starting with the mining and processing of the raw materials, continues with cell component manufacturing, battery pack manufacturing, electric vehicle manufacturing and ends with recycling of the lithium-ion battery packs.

China produced 80% of global battery grade raw materials in 2019. China’s share in cell component manufacturing accounted for 66% of global production in 2019. China produced 73% of battery cells globally in 2019. It is obvious that China is the leader in processing of raw materials, in cell component manufacturing and cell manufacturing, but only 23% of global supply of all battery raw materials came from China (6). Europe's share of capacity of cell component manufacturing accounted for only 6% in 2019 (7).

Key raw materials used to make EV batteries

Lithium and cobalt have the biggest supply risks among the metals used in EV lithium-ion batteries, whereas aluminum has the lowest. Medium supply risks exist for manganese, iron, nickel and copper. 

Lithium

Lithium is the key component in every lithium-ion battery, all cathodes of lithium-ion batteries contain the lithium. It is expected that demand for the lithium carbonate (Li2CO3) that is used in lithium-ion batteries, will start to increase again. Australia, China and Chile accounted for 88% of global lithium production in 2019 (8). Lithium is a mineral produced from brines (Argentina, Chile Bolivia) or hard rock sources (Australia). China produces from both brines and hard rock sources. Total world lithium production was 82000 tonnes in 2020.

The current price of lithium carbonate (99.5% Li2CO3 battery grade) is 14240 USD per tonne.

Cobalt

The most cathodes of automotive lithium-ion batteries contain cobalt. More than 70% of the world’s cobalt is produced in the Democratic Republic of the Congo (DRC) and 15 to 30 percent of the cobalt is produced by artisanal and small-scale mining there in DRC (9). Russia, Cuba, Australia and Canada, the next largest supply countries, accounting for just 13% of global supply. Total world cobalt production was 140000 tonnes in 2020. There are preferred chemistries with reduced cobalt content with some compromise in performance. A successful combinations are NCM532, NMC622 and NMC811. The current price of cobalt is 42535 USD per tonne.

Nickel

Nickel is the key component in lithium-ion battery that have NCA and NMC cathodes. There is the focus in low cobalt batteries like NMC 811 and even newly proposed NMC 9.5.5 batteries (with 9 parts of nickel and 0.5 parts of cobalt and manganese). Nickel rich cathodes will have certainly an impact on nickel consumption and the nickel market. Demand for the nickel is expected to grow over the coming years, it is driven by using the nickel in EV’s lithium-ion batteries. Total world nickel production was approx. 2.5 million tonnes in 2020. The biggest producents of nickel are Indonesia, Russian and Philippines. The current price of nickel is 17619 USD per tonne.

Second life of lithium-ion Batteries

When electric vehicle batteries degrade to 70–80% of their original capacity, it is necessary to replace them because the residual capacity becomes insufficient for automotive use. These used batteries could be removed and remanufactured. Poor-quality cells would be recycled, but high and average-quality cells might be reused. These cells that passed the quality test can be used in the energy storage application and live their second life. Such energy storages allows renewable energy sources (solar panels, wind turbines, etc.) to store generated electric energy and support the electric grid with electricity during peak demand hours.

Recycling

There are several ways to recycle lithium-ion batteries. Generally, two recycling methods for lithium-ion batteries exist hydrometallurgy and pyrometallurgy.

Hydrometallurgy is based on aqueous chemistry, typically at low temperatures, typically have a high extraction rate, a high metal selectivity and a low energy consumption. Hydrometallurgical processes consists of several steps. The metals are dissolved with the help of an acid or salt. Another step is purification where metals are separated via selective chemical reactions. In the last step, the metals are recovered from the solution as a solid product in a form of metals, salts or a compound, by crystallization, electrochemical or electrolytic reduction, etc. This process needs large plant sizes, there are utilized concentrated acids, which easily generates large amounts of waste solutions. Under the optimal conditions, the recovery percentages of Ni, Co, Mn, and Li can reach 98%, 97%, 98%, and 89%, respectively.

Pyrometallurgy needs high-temperature processes such as roasting or smelting for recovering cobalt, nickel, copper, aluminium and iron. Pyrometallurgy has advantages such as high reaction rates, small plant size for a given throughput, and a high overall efficiency. The high temperatures needed in the processes lead to high energy consumption and emissions. In addition, the recovery of lithium is very difficult. These processes often only produce intermediates that require further hydrometallurgical process.

1, https://ec.europa.eu/clima/policies/transport/vehicles_en

2,https://www.automotiveworld.com/news-releases/zsw-electric-cars-on-the-rise-global-count-climbs-to-10-9-million/

3, https://www.statista.com/statistics/970958/worldwide-number-of-electric-vehicles/

4,https://ihsmarkit.com/research-analysis/threefold-increase-in-recycling-needed-to-help-meet-2030-deman.html

5, https://www.iea.org/reports/hydrogen

6,https://www.benchmarkminerals.com/membership/china-controls-sway-of-electric-vehicle-power-through-battery-chemicals-cathode-and-anode-production/

7,https://www.spglobal.com/marketintelligence/en/news-insights/blog/top-electric-vehicle-markets-dominate-lithium-ion-battery-capacity-growth

8, https://www.nsenergybusiness.com/features/top-lithium-producing-countries/

9, https://www.cfr.org/blog/why-cobalt-mining-drc-needs-urgent-attention

10, https://pubs.usgs.gov/periodicals/mcs2021/mcs2021.pdf

11,https://www.researchgate.net/publication/267931433_Hydrometallurgical_process_for_the_recovery_of_metal_values_from_spent_lithium-ion_batteries_in_citric_acid_media