Lithium rechargeable

About

Anode: graphite, various
Cathode: lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, various
Electrolyte: various
Type: rechargeable
Nominal cell voltage: 2.0 - 3.85 volts
Energy density: 250 - 700 W·h/L
Monthly self-discharge rate: 0.35 - 2.5%

Pros:

Performance - one of the best performing battery chemistries available
Longevity - one of the best available
Charge responsive - lithium-ion responds very quickly to both charging and discharging needs
Size - can be small yet powerful thanks to an excellent energy density
Versatile - Can be adapted to practically any voltage, power and energy requirement

Cons:

Volatility - lithium-ion batteries are a fire hazard
Toxicity - many lithium-ion batteries contain toxic electrolyte materials

General information on lithium-ion

Lithium-ion rechargeable batteries are increasingly popular today, used in mobile phones, e-cigarettes, computers, electric vehicles, and much more (including military and aerospace applications). They were first made commercially available in 1991 by Sony following decades of research and experimentation. A few decades more research has helped this battery chemistry excel above all others in its performance and longevity while also bringing down the price considerably.

Lithium-ion batteries are so named due to the particular use of lithium-ions within the cell. These ions can travel through the electrolyte and other internal membranes of the cell that otherwise block the flow of electrons. While a lithium-ion battery is in use, electrons flow from the anode, through the device circuit, to the cathode, just like any regular battery. However, at the same time lithium-ions travel from the anode directly through the electrolyte to the cathode, thus keeping electroneutrality within the cell. When the battery is being charged, this flow is reversed, loading the anode with lithium-ions once again.

Just like lithium primary, there are many chemical variants within the lithium-ion family. The most common format for high-end handheld electronics is lithium polymer with a polymer gel electrolyte and a lithium cobalt oxide (LiCoO2) cathode.

Cell structure

The internal elements of batteries can be arranged in various ways to optimise usage. This is one of the reasons there are so many differently shaped batteries in use today. In general, the cathode, anode and separators are either rolled around one another (for cylindrical batteries), folded into geometric layouts (for prismatic batteries) or stacked on top of one another (in the case of pouch batteries). Prismatic geometry was developed in the 1990s in response to consumer demand for thinner, smaller, more powerful technology. Each option has its pros and cons - mostly a balance between performance and volatility.

Most common applications

Rechargeable lithium-ion batteries can mostly be found in mobile devices, such as phones, tablets and laptops, as well as in electric vehicles.

Lithium batteries for electric vehicles

Electric vehicle batteries use various materials depending on the desired balance between engine performance and unit cost. The technology is also evolving rapidly, leading to quickly outdated cell technologies. For example, old Tesla Model 3 and Model X cars ran on NCA lithium nickel cobalt aluminium oxides (LiNi0,84Co0,12Al0,04O2), while newer standard-range Teslas use LFP batteries. Lithium nickel manganese cobalt oxide, otherwise known as NMC or Li (NixMnyCo1−x−y)O2, has also been used by several companies such as Nissan, Chevy and BMW.

Why recycle lithium rechargeable batteries?

There are 3 key reasons to recycle lithium-ion batteries. First, safety - these batteries can lead to fire hazards due to thermal runaway - a feedback loop whereby an increase in temperature changes the conditions in the cell leading to a further increase in temperature, and so on. Damaged batteries can spontaneously combust, and the world has already seen too many instances of exploding phones and e-cigarettes resulting in fire and injuries.

Second and third, responsible resource management and the tremendous upcoming surge in quantity of lithium-ion batteries, which will quickly lead to a waste management challenge as well as economic opportunities. With the production of lithium-ion batteries set to double over the next five years, the recycling of these cells is more important than ever. Lithium-ion is also the battery of choice for electric vehicles, another market set for rapid growth.

This dramatic increase in the near future will put a strain on the planet’s supply of lithium. Lithium mining is less harmful than many other mining practices, but is still detrimental to our planet. Thus, the more we can ‘close the loop’ on lithium-ion batteries, the better. Lithium batteries can contain other useful metals too, such as nickel, cobalt, and manganese, which are otherwise extracted from the earth under careless, exploitative, and inhumane conditions.

A costly construction

Traditionally, at least one third of the production cost of a lithium-ion battery is the materials, given that these cells contain high amounts of valuable metals in various forms. However, battery manufacturers are increasingly developing chemistries with fewer or no valuable metals to reduce costs. For example, LFP batteries no longer require cobalt or nickel, and emerging sodium-ion batteries use sodium instead of lithium. While these innovations make batteries cheaper and more sustainable, they also pose new challenges for recycling, as fewer valuable materials are present to recover.

The danger of EV batteries

Of particular concern is how to recycle Lithium-ion batteries from vehicles that have been involved in accidents. Fire services are developing protocols around the handling of damaged EV lithium-ion battery packs and their safe transportation and handling in order to get them to recycling facilities.

Process highlights

At present, Lithium-ion batteries for both handheld devices and electric vehicles are often processed in the same facility, with roughly the same flow. The main difference is dismantling EV batteries vs shredding smaller batteries. The processes are also fine-tuned to accommodate the specific chemistry and quantities found in the different lithium-ion battery strains.

Discharging

The first step in recycling is safety, as lithium-ion batteries must be handled carefully to avoid thermal runaway. Traditionally, batteries are fully discharged before shredding, which can be done using a resistor or by submerging the cells in liquid nitrogen or a salt-water solution to induce short circuits and a rapid discharge. However, discharging is labour-intensive and costly, so some recyclers use alternative approaches. In these cases, the organic materials in the battery are first removed thermally before shredding, or the batteries are shredded directly under water to prevent the presence of oxygen.

Disassembly and comminution

Disassembly is a next important step when dealing with specifically constructed lithium-ion cells, such as those found in electric vehicles. Manual disassembly allows for a clean separation of particular parts of the product, improving the purity of output streams, but it’s also labour intensive.

Alternatively, comminution is typical for smaller cells. This is often carried out in a rotary shredder in a CO2 and argon rich atmosphere to convert any released elemental lithium to lithium carbonate, a less volatile compound form.

Physical separation

A relatively typical physical separation process follows, aimed at retrieving output streams for:

Plastics and paper
Black mass (containing lithium, nickel, cobalt, manganese and electrolytes)
Steel battery casings and fixtures
Metal alloys such as aluminium and copper used in electrode foils.

Pyrometallurgical and hydrometallurgical processes

A combination of pyrometallurgical and hydrometallurgical processes are then used for further recycling. Vacuum pyrolysis may be used to separate out the metal alloy stream to its individual components. If the black mass is also treated by pyrometallurgy, lithium may be part of the slag output, which can then be further treated to extract the lithium or go straight to construction uses. Alternatively, the black mass is treated by a series of hydrometallurgical processes to leach out the heavy metals from the carbon graphite content. From here, lithium, cobalt, nickel and manganese are each separated through solvent extraction and recovered as salts, which can then be used as the base material for new batteries.

If pyrometallurgical processes are used for the treatment of lithium-ion batteries, organic materials like the plastics used for electrode separators will be consumed as fuel to produce energy for the pyrometallurgical smelter and thus cannot be recovered.

Cobalt may be recovered hydrometallurgically from lithium-ion batteries via electrolysis or precipitation as Co(OH)3 through the addition of sodium hypochlorite.

End products

Polymer plastics
Papers
Steel
Lithium salts
Lithium enriched slag
Cobalt sulphate
Nickel sulphate
Manganese

Unfortunately the cobalt, nickel and lithium end products are not in a pure enough form to be directly reused in the creation of new batteries. They need to be further refined into PCAM (precursor cathode active material) and then CAM (cathode active material).

Future trends

There are many developments in the area of lithium-ion batteries. With regard to production, non-flammable (solid state) electrolyte options are being researched to ease the danger of combustion. Prices are improving through the substitution of (expensive) cobalt by cheaper alternatives, as is efficiency and longevity.

With regard to recycling, hydrometallurgical processes are a growing trend in order to extract reusable lithium from used batteries. Many new methods are being tested on laboratory scale, and governments around the world are providing strong incentives for businesses to innovate in the field of lithium-ion battery production and recycling.

Biohydrometallurgy is an exciting and unique avenue currently being explored. A bio-leaching process has been researched that recovers 100% copper and lithium, and 75% aluminium using various acids and living bacteria! The bacteria consumes waste battery compounds and excretes metals and metal oxides. This process is extremely low cost and low emission, and can work on relatively impure input streams, but it is also presently far too slow to be commercially viable.

Why don’t recyclers recover more lithium from these batteries?

There are two principle reasons why current recycling methods often don’t recover the lithium from these cells:

Lithium-ion technology continuously changes, which means recycling processes must also change regularly. Thus, more specific, lithium-focused methods are at risk of becoming outdated.
Reclaiming lithium from used batteries is about five times more expensive than mining it from the earth, making it economically unsustainable at this point in time. Currently, the prices paid for Lithium do not reflect the environmental externalities and impacts on communities where the material is mined.

However, government subsidies and legislation are helping to turn the tide, and pyrometallurgical methods are slowly being transformed to include hydrometallurgical steps to reclaim lithium. What we outline here is a general approach used on an industrial scale by several facilities around the world.