Evolving input trends for end-of-life lithium-ion cells and its relevance for battery recycling

The trend of Lithium-ion cell stock coming for recycling is an important consideration every recycling company needs to account for. This aspect directly links to the economics of battery recycling operations as different types of cells (in terms of form factor and cathode material used) have different unit economics linked to them.

This article by Rahul Bollini discusses the changing trends of lithium-ion cell chemistries.

The need to understand incoming cell stock trends

Different raw materials are used for the casing of different form factor cells.

• Cylindrical can is made up of steel coated with nickel.

• Pouch case is made up of aluminium, polyamide and polypropylene layers.

• Prismatic can is made up of aluminium.

The electrolyte content is also different for each form factor, which means different Lithium content. This question is closely related to operation planning, as most companies in their initial stages have a single line of operation that requires continuous operation with a consistent type of Lithium-ion cell input. This is necessary to ensure a uniform composition of black mass is generated during the mechanical separation, which is the first process in recycling.

A test certificate is issued to assure black mass buyers that they receive what they pay for. Black mass pricing is based on its material composition. The companies need to plan the batches with decent input volumes of Lithium-ion cells with the same characteristics to get a predictable black mass output in terms of material constituents. Hence, it becomes important for them to understand the trends of incoming types of Lithium-ion cells.

Let us explore the type of Lithium-ion cells that have come and gone, the type of Lithium-ion cells in circulation, and the type we can expect coming in the future.

LCO (Lithium Cobalt Oxide)

• Due to its high voltage and stability, given its high cobalt content, LCO is used in portable devices such as mobile phones and laptops.

• It is the most expensive battery type and uses graphite anode.

• The black mass value of the LCO cell is highest due to its high cobalt content.

LMO (Lithium Manganese Oxide)

• LMO offers high power delivery but failed to impress the market due to higher degradation at high operating temperatures. The cells become less uniform after about two years, drastically dropping the EV range. It was featured in the first-generation Nissan Leaf.

• Its price is very low due to the use of low-cost Manganese and the lack of Nickel or Cobalt.

• It delivers a nominal voltage of more than 3.7V.

• It has now been relaunched in combination with NMC and is doing well in the fast-charging market segment. Many electric buses in India use this mix of LMO + NMC.

NMC (Lithium Nickel Manganese Cobalt Oxide)

• Very popular in the electric 2-wheeler segment. NMC was also widely used in the electric car segment until recently when LFP started replacing NMC.

• Initially launched as NMC 111 – ratio of one part nickel, one part manganese, one part cobalt.

• Then came newer variants such as NMC 442 (short-lived).

• NMC 532 (very popular today in the Indian market in 2600mAh 18650).

• NMC 631 (higher voltage cell, 3.75V nominal voltage).

• NMC 622 (used in pouch and prismatic cells).

• NMC 712 (popularised by LG).

• NMC 811 (popular with Graphite and Silicon Graphite).

NCA (Lithium Nickel Cobalt Aluminium Oxide)

• Tesla popularised NCA until they recently adopted LFP for low-range cars.

• It is used in high-range vehicles and is more expensive than NMC. Its thermal runaway is more challenging than NMC, so it needs a good thermal management system.

• Most premium electric 2W companies use NCA cells. These variants contain Silicon in their anode to enable higher energy density.

• Due to its ability to deliver high power when put in a high-power cell design, NCA is used in dronebatteries.

LFP (Lithium Iron Phosphate)

• LFP is considered favourable because of its low cost, safety, and longevity. However, its gravimetric and volumetric energy density are not the best in the market.

• I believe LFP is not good news for recycling companies because of its lack of Cobalt or Nickel. It also has lower Lithium content per Kg of cells than other cells.

• LFP is highly preferred in Indian electric cars and 3-wheelers.

• 2W companies are slowly planning to shift to LFP after the FAME subsidy was reduced.

• Most upcoming Indian cell manufacturing companies consider LFP as their first choice because of its growing demand and also because its constituents are easier to source.

Various cell models are available in the market, and understanding their chemistry is key for recycling companies. Let us try to understand the cell type by model name. For example, any cell model that begins with IF is a LFP cell.

The LFP cylindrical cell model name will begin with IFR, and the pouch and prismatic cell model name will begin with IFP. R in IFR indicates that it is a round cell, and P in IFP indicates that it is a pouch or prismatic cell.

New Lithium-ion cell chemistries to watch out for

• LCO + Silicon Graphite: It has already begun production for mobile phones to enable higher capacity for the same space availability.

• NCMA (Lithium Nickel Cobalt Manganese Aluminium Oxide): Known for being stable despite using high Nickel content (around 90%) because it contains both Manganese and Aluminium. Popularised by LG, it has already entered the market for electric cars.

• NMC 9.5.5 (Lithium Nickel Manganese Cobalt Oxide): Trials are going on for use in portable applications, given its high energy density. Gravimetric energy density is close to 300Wh/Kg.

• LMFP (Lithium Manganese Iron Phosphate): On trial in the market to compete with NMC, given the ability of LMFP cells to have similar voltage and pass the nail penetration test. Some companies are mixing NMC and LMFP in various ratios, and they still call it an LMFP cell.

A test certificate is issued to the black mass buyer for assurance, as even though the cell model and cell form factor look similar, the composition of the raw materials can differ. For example, the amount of conductive carbon additive can be different in the electrode composition (cathode and/or anode), thereby affecting the content of other materials present in a given quantity of black mass.

About the author:

Rahul Bollini is an R&D expert in Lithium-ion cells with 8 years of experience. He founded Bollini Energy to assist in deep understanding of the characteristics of Lithium-ion cells to EV, BESS, BMS and battery data analytics companies across the globe. Rahul can be reached at +91-7204957389 and bollinienergy@gmail.com.

Also Read: KYC(Know Your Cell) – Various ways to understand lithium-ion cell quality