The electrification of the vehicle fleet is gathering pace. So far in 2020, 1 in 4 vehicles sold contains a traction battery (combination of all types of electrified vehicles).
Tens of thousands of tonnes of batteries have already been placed on the market and eventually they will all require recycling. Recycling of automotive batteries requires a whole end of life eco system to be installed – such as training of personnel, battery removal capabilities, battery triaging capabilities, battery transportation, battery processing during recycling and finally metal and other material refining and recovery capabilities.
WMG is working alongside a number of industrial partners to make this a reality and also carrying out cutting edge research to enable more efficient recycling.
• What are the materials in Li-ion EV batteries that are most important in terms of their ability to be recycled whether in terms of value, legal requirements or potential for re-use?
Legally, the batteries must be recycled according to the European Directive 2013/56/EU, also known as the ‘Battery Directive’. The Battery Directive regulates the production and recycling of all types of batteries placed on the EU market.
In terms of recycling, the batteries are split according to chemistry. Automotive traction batteries (batteries that are used in the propulsion of a vehicle) are predominantly of the lithium ion chemistry and the Battery Directive stipulates that a minimum of 50% of the battery material must be recycled by mass. Under the Battery Directive, a material can only be considered recycled once it becomes a product that can be reintroduced onto the market. This means that a recycler must not only account for their own processing efficiencies but also that of their customers, until the material can be used again as a product.
In terms of the importance of materials to be recycled, there are three factors to consider; (i) value of the material (ii) ability of a material to be recovered and (iii) ability of the material to be recycled. The value of the material is always the most important starting point as the most valuable components will be targeted first by the recyclers. The ability of a material to be recovered refers to the difficulty (or the ease) with which it can be separated from the other components using existing technologies. Finally, the ability of a material to be recycled refers to the difficulty or ease with which the recovered product can be purified or transformed so that it can go back into the original application or if not then another application.
Using the above criteria, the most important materials within lithium ion batteries are the metals as they fit all three criteria. In terms of value, they all have a set price according to the London Metal Exchange (LME) and should the purity of recycled product attain LME standards, it can be sold at LME price. The separation of the metals from the other components is also quite easy and can be done using widely available technologies such as magnets or eddy current separators. The most expensive metals in lithium ion batteries are found in the cathode powder as metal oxides. As they are metal oxides and not pure metals, they must be recovered hydrometallurgically, meaning that the metal oxide is first broken down using acids and then the different metal ions are separated from each other.
The non-metallic components are much more difficult to recycle given current technologies and market conditions. The main hindrances are the lack of value ad market for these products. For example, it is really easy to separate the plastics contained within the batteries but as they have little to no value it is much more difficult to sell them on for a profit and even more difficult to recycle it into a new product. In the future this will change as the larger volumes will enable niche markets to develop.
• Are the methodologies/technologies for recycling Li-ion batteries well-established and proven or is there potential for their enhancement?
There are two main approaches to lithium ion battery recycling; high temperature smelting (pyrometallurgical) and mechanical shredding followed by material separation. Enhancements to recycling technologies can be made in three ways; (i) improving process throughput, (ii) improvements to process recovery efficiency and (iii) improvements to product purity. For automotive lithium ion battery recycling, improving process throughput is currently the biggest challenge as discharging and dismantling the battery packs is a time consuming process and it applies to both pyrometallurgical and mechanical shredding processes. Improvements in recovery efficiency applies mainly to processes based on mechanical shredding since pyrometallurgical processes combust many of the materials that make up a battery, such as all the plastics, electrolyte and graphite. For mechanical shredding processes, such improvements are possible and will be developed and implemented once markets for such products become available.
• What causes the difference between the relative values of the cathode and anode current collector materials in new and end-of-life batteries, 51 per cent and 93 per cent respectively – what actually are the materials involved?
The anode and cathode are both metal foils coated with powders. The anode is a copper foil with a graphite coating whilst the cathode is an aluminium foil coated in a lithium-transition metal- oxide powder. The transition metals may be cobalt, nickel, manganese or a combination of the three such as lithium nickel manganese cobalt oxide (LiNi0.33Mn0.33Co0.33O2). It is the cathode chemistry that generally differentiates the different types of lithium ion batteries. The difference in value between the new and the scrap material is mainly down to the costs involved in the material processing. The value of the new material is determined by the metal and non-metal contents (such as graphite, carbon black, binders etc) as well as the labour and energy required for processing the material to achieve the stringent specifications required by battery manufacturers. For end of life anode and cathode, the value is determined mainly by the metal content and in particular the lithium, cobalt, nickel and copper and the aim of the recycler is to recover these metals for less than their value so they can be sold for a profit.
• Do you foresee any changes in Li-ion battery chemistry that could significantly impact their recyclability?
A number of different chemistries are in development such as solid state lithium ion batteries, sodium ion batteries or a slightly different chemical make-up of the existing chemistries that uses a smaller amount of one metal and more of another (such as replacing cobalt with nickel or manganese). In all cases, the most important factor determining the recyclability is the value of the metals that go into the batteries. Ironically, the move towards batteries with cheaper metals will make them less recyclable as the work required to recycle the metals will cost more than the value of the metal itself. In some cases (such as solid state lithium ion batteries), the profitability of the recyclers could increase as the batteries will be a lot safer to process without the flammable electrolyte and therefore cheaper to recycle.
• There seem to be several different basic processes for recycling Li-ion batteries – which are the ones of most relevance to automotive batteries and why?
As mentioned above, the lithium ion battery recycling processes can be split into two types; pyrometallurgical and those based on mechanical shredding. Both the processes are capable of recycling automotive traction batteries. New processes are almost exclusively based on shredding and material separation as they are much cheaper to set up, much less energy intensive and give higher recycling efficiencies.
• What are likely to be the major responsibilities of vehicle manufacturers in a scenario in which there is large scale recycling of Li-ion batteries – what, for instance, do you mean by your observation that vehicle manufacturers ‘must provide battery passporting data to vehicle/battery recyclers allowing for accurate triaging?’
As vehicle recyclers are bound by law to comply with the Battery Directive, they must ensure their batteries are recycled in a safe and efficient manner since ultimately they are responsible for cost of recycling the batteries. It is in their best interest to enable recyclers to attain as much value from the battery as possible. One of the ways in which they can do this is to provide ‘battery passporting’ data to the recyclers. In practice this means allowing the recycler to access the history of the battery enabling them to attain the state of health of the battery and allowing for a rapid decision to be made as to the treatment route, whether it be re-use, remanufacture or recycling. Failure to do this will add additional costs to the recyclers, decreasing the value they can attain from the battery and perhaps even charging the vehicle manufacturer for the recycling.
• Are there any useful lessons for the recycling of automotive Li-ion batteries from the recycling process for Li-ion batteries for other applications?
Recycling of lithium ion batteries is the same whether it is from portable applications or automotive applications. At their most basic level, automotive batteries consist of smaller cells, these could be cylindrical (same format cells found in laptops and Tesla vehicles), pouch or prismatic. The cells are grouped together into modules and the modules are grouped together to make the battery pack. The cells and modules are grouped together in series and/or parallel to increase the current and voltage, allowing more power to be drawn from the battery. When recycling automotive batteries, the packs are discharged and dismantled into modules or cells before they are processed.
• Are Li-ion batteries the only type of battery chemistry used for automotive applications and if not roughly what proportion of automotive batteries do they currently provide?
There are five types of vehicles that use batteries for electric propulsion, these are shown in the table below;
|Battery Electric Vehicle (BEV)||Vehicle powered only by battery/electric motor. Battery capacity of 25kWh – 100kWh. Battery weighs 300kg – 600kg. Battery provides a range between 110 – 350 miles|
|Plug in Hybrid Electric Vehicle (PHEV)||Vehicle can be powered by both the engine and the battery/electric motor. Vehicle has a range of 20-30 miles on battery power alone. Battery capacity of 8-14kWh. Battery weighs between 80-200kg|
|Range Extender Electric Vehicle (REEV)||Vehicle is powered by battery/electric motor. Vehicle also has a small engine that acts as a generator to recharge the battery and allow for long range driving. Vehicle has a range of 75-125 miles on battery power alone. Battery has a capacity of around 30kWh. Battery weighs around 250kg|
|Hybrid Electric Vehicles||Battery/electric motor is mainly there to assist the engine with acceleration or during demanding work. Vehicle can be driven on battery alone but the range is very small. Battery has a capacity of 1-2kWh. Battery mass ranges from 25-60kg|
|Mild Hybrid Electric Vehicles (MHEV)||Battery is there solely to assist the engine in acceleration or other demanding work. Vehicle cannot be driven using the battery. Battery has a capacity of around 0.4kWh. Battery mass is around 10kg|
Of the five types mentioned above, almost all the vehicles use lithium ion batteries of varying chemistries such as lithium iron phosphate for HEV and MHEV and nickel manganese cobalt oxide (NMC) for PHEV and BEV. Toyota, which has the largest market share in HEVs, is the only major vehicle manufacturer to still use non lithium ion battery technology. It still prefers to use nickel metal hydride (NiMH) batteries for its HEVs which accounted for 66% of Toyota’s passenger vehicles sales in the UK in 2019. Toyota has over 20 years of experience in NiMH battery technology and the batteries are perfectly suited to the high power requirements of HEVs. For vehicles that require longer ranges, a lighter and more energy dense technology is required and that is why even Toyota uses lithium ion battery technology for its PHEV models (Toyota does not have a BEV model yet).
Find out more about WMG's Energy research here.
Content originally published in Automotive Manufacturing Solutions here.