With the limited numbers of electric vehicles (EV) that have been sold to date and the fact that their batteries can last for seven years or more, the environmental impacts of EV lithium-ion battery recycling have not yet become a pressing issue. Nevertheless, the overall environmental benefits of converting vehicles from internal combustion to battery power are widely publicised and the change-over is being mandated by legislation to help meet global greenhouse gas emission reduction targets. While all of this is deemed to be good for the world and its inhabitants, it is less often considered that there can still be negative impacts associated with lithium-ion batteries. In terms of the environment, it is easy to think that the move from fossil fuels must undoubtedly offer major benefits and, in many areas it does, with the prospect of zero local emissions, improved air quality and the concomitant related health improvements being good examples.
More specifically, in terms of circular economy thinking, it is now generally agreed that end of first life EV batteries should, where possible, find use in secondary applications and then ultimately be recycled to recover their valuable raw materials. However, when it comes to recycling, there are significant challenges, since EV batteries are heavy, complex and disparate assemblies containing a wide range of materials. The key recyclable raw materials, i.e. the ones that have a sufficiently high value to make them attractive to recover, are typically found inside the battery cells themselves. Gaining access to these materials and then being able to recover them in a form suitable for reuse is thus often difficult and expensive. In fact, the cost of recycling can sometimes actually exceed the recovered value, thus deterring such activities using conventional technologies.
As a result, there has been much work to develop new recovery technologies for the key metals, such as lithium, nickel and cobalt, found in lithium-ion batteries. Unfortunately, while various novel techniques have been successfully demonstrated, the actual processes can often be complicated and expensive to operate. This means that, at least for the immediate future and from a technical perspective, the already well-established metal recycling processes that have been used over many years seem likely to be employed for treating lithium-ion batteries. These basically involve dismantling and mechanical separation, followed by thermal and/or chemical treatment stages to extract the target metals. Some of these are already in operation commercially, but improvements need to be made to ensure broader economic viability and to minimise the negative environmental impacts such as energy use and chemical consumption, along with the generation of expensive to treat waste products and effluent emissions.
However, despite these process considerations, there is still a very strong case for recovering valuable metals. For example, it has been shown that recycling and reusing cobalt can be more sustainable than obtaining it via primary extraction. In this case, recycling can be beneficial both economically and environmentally. The recycling of cobalt requires significantly less energy and produces fewer greenhouse gas emissions than its production from raw materials. It also helps to maximise the use of natural resources and prevents valuable materials from being landfilled. Additionally, increased recycling can reduce the reliance on imports of raw materials, thus lowering carbon dioxide emissions caused by transportation.
Unfortunately, in the case of lithium, work to date has confirmed that it is not economically viable to recover it from recycled batteries, especially as they only contain a relatively small quantity of the metal. Lithium is also inexpensive compared to other key battery metals such as cobalt and nickel. It has been reported that the average cost of the lithium, as a percentage of the overall battery production costs, is less than 3%. In fact, it can cost up to five times as much to recycle lithium as it does to produce it from the low cost, well established brine-based processes. Therefore, very little lithium used in batteries is completely recycled. This is bad news from an environmental perspective and it seems likely that, if lithium is ever to be recovered and reused, it may have to be mandated via suitable legislation.
Hopefully, the recycling of lithium, cobalt and other metals should be able to offer environmental benefits, while also enabling battery makers to reduce the consumption of finite resources and to establish relatively local supplies of these key materials. However, even if they can be recovered, this still leaves a lot of other materials, many of which are either not reusable, or which can’t be economically recovered. Examples here include the various plastics, rubbers and sealants used in the external casings, as well as in the structure of the battery itself. Many of these can be removed and sorted during the disassembly processes and might, therefore, be recyclable, e.g. the polypropylene and polyethylene used for separators. Unfortunately, in the structure of a working cell, there are other less desirable materials such as the critically important electrolyte that comprises lithium salts, and some other additives, dissolved in organic solvents. These materials are not particularly nice to handle and the electrolyte solvents, being organic, are flammable and capable of producing noxious gases during recycling operations.
While it is generally agreed that there must be more use of recovered materials in the fabrication of new lithium-ion batteries, it can be seen, even from just the above brief overview, that there are both positive and negative impacts associated with recycling. At the moment, the negative impacts present a major constraint to recycling and new technologies and more efficient approaches are needed.
In summary, there are many factors influencing the specific decisions about EV-battery material recycling. Environmental impact considerations are clearly important, but only part of a much bigger picture. It therefore seems likely that, without some widely agreed policies and globally implemented legislation, the key determinant is more likely to be cost. New and improved recycling technologies are needed, especially as the number of batteries available for recycling increases in the future. More positively, there are estimates suggesting that the production of electric vehicle lithium-ion batteries from recycled materials could reduce their total cost by around 20%.
Written by Martin Goosey, Envaqua Research Ltd.