Lithium-ion batteries have become a great aspect of green mobility due to their friendly impact on the earth and its nature. But one of the negative aspects is the waste from the lithium-ion batteries which is nearly 250,000 tonnes or half a million cubic. As more batteries are being manufactured the challenges of managing the waste have become a major concern. As currently, no recycling method exists which is both efficient and profitable enough to be sustainable. And the question rises, what needs to be done with the next generation of end-of-life batteries? As the average battery only guarantees to last only eight years.
One of the greatest issues driving lithium-ion battery recycling is waste management but it is not correct to say that all of the batteries being manufactured today are headed for the landfill. When a lithium-ion battery comes to the end of its life, it still retains around 80% of its charge – and while that’s not enough to serve an electric vehicle, it’s good enough for a variety of different applications, such as energy storage. These second-life batteries could be used for at least 10 years. This kind of reuse is preferable in the first instance to recycling, because they’re extremely valuable – and recycling is costly. ‘The material in a Tesla battery, for example, is worth around $1500 (£1200) – but the market value is between $10,000 and $15,000.
For an instance, the world’s biggest operator of telecommunication towers, China Tower, intends to replace the lead-acid batteries used for backup power at almost all of their 2 million tower base stations with second-life lithium-ion batteries. That’s 54GWh of battery storage – or around 2 million batteries. In this way, reuse can play a role in adding value and providing the recycling industry with time to pull together the necessary infrastructure to recycle batteries at scale. But with the total amount of lithium-ion batteries is expected to reach 7.8 million tonnes per year by 2040.
Difficulties in recycling
Much of the recycling that takes place today is done through a combination of pyrometallurgy and hydrometallurgy, a process that leaves more to be desired. While the process recovers some of the most valuable metals in the battery, much of the other valuable material is lost. ‘Basically, you throw the battery into a smelter, and you get a mixture of alloys out the bottom – typically nickel, cobalt, and copper. ‘The lithium and aluminum get oxidized and go to the slag – they aren’t economical to recover.’ After the lithium and aluminum get sent to the landfill, we are left with the metal alloys – these then have to be treated hydrometallurgically to extract the maximum value, breaking down the cathode’s crystal structure and leaching the different ions out of the battery to end up with the precursor salts like nickel sulfate and cobalt sulfate which you can use to manufacture new batteries. ‘Cobalt is by far the most valuable product. ‘But as automakers are moving towards battery chemistries with less and less cobalt in them, the valuable product you’re getting out of the leaching process keeps decreasing.’
Numerous issues complicate the development of a more efficient process. A fundamental problem is that these batteries simply aren’t designed to be recycled, they’re designed for high performance and longevity, essential capabilities of a battery that could be impaired at the expense of designing a battery that is more recyclable. A lithium-ion battery pack is made up of several thousand cells grouped in modules, with each cell containing a cathode, anode, separator, and electrolyte. Cathodes generally consist of an active transition metal oxide powder mixed with carbon black and glued to an aluminum-foil current collector with a compound such as poly (vinylidene fluoride) (PVDF). The anodes contain graphite glued to a copper foil with PVDF, and the electrolyte is usually a solution of LiPF6 salts.
The state of recycling today
Even with a lack of design for recycling, researchers are looking at ways to maximize recovery. A purely hydrometallurgical process would be more efficient– that is, using aqueous solutions to leach out the valuable metals from cathode material after shredding. That’s usually carried out using a combination of sulfuric acid and hydrogen peroxide, with the peroxide working as a reducing agent to convert insoluble Co (iii) materials into soluble Co (ii). After leaching, the cobalt and lithium can be recovered as salts through precipitation by changing the pH of the solution. That process leaves you with high-purity starting materials which can then be used to manufacture new batteries. But while hydrometallurgical processes recover more valuable materials than purely pyrometallurgical ones, the value that comes from the actual cathode material is lost. That means that while it’s useful for cathodes that contain a large amount of cobalt like lithium cobalt oxide – hydrometallurgical processes can recover up to 70% of these cathode’s value – it’s less useful for cathodes that are less cobalt-rich, where most of the value lies in the manufactured cathode oxides themselves, rather than in the raw materials.
Without recycling, we could be looking at a mountain of battery waste
In cases where the value of the raw materials is lower, it is possible to recover the valuable cathode itself. Through a process known as direct recycling. Direct recycling is based on preventing the crystal structure of lithium-ion battery cathode from being broken down – the benefit is that you maintain the value of what goes into transforming the raw materials into a cathode, which can be quite significant. Direct recycling has another benefit, in that it also allows other valuable components such as aluminum and copper foils, salts from the electrolyte, and graphite from the anode to be recovered. In direct recycling, the battery is again shredded and the black mass a mix of cathode and anode powders – is recovered. ‘When you get the powders back, they’re coated in polymers.
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