Battery end-of-life analysis: smart solutions for battery re-use and second life

A cura di Carlo Gulizia

In 2017, the global production of electric vehicles (EVs) reached and overcame the million of units, following a positive trend which should lead to the revolution of the worldwide vehicle fleet. Components and technologies required in this new concept of vehicle involve huge transformations in the automotive sector and impose new big questions to be answered.

How to produce electric energy to power the EVs? How to renew the already existing infrastructures to adapt them to those new technologies? How to dispose the new types of waste they originate?

In this article, EV battery packs end-of-life (EoL) solutions will be analyzed together with the problem of materials required for electrodes production.

 

BATTERY RECYCLING: WHY?

A battery is an energy storage system in which chemical energy is converted into electricity and used as a source of power. That technology is already widespread and used for other applications than mobility, so why should Lithium Ion batteries disposal be a problem?

To power an electric car for 300 km, a battery pack of about 250 kg, made up of common metals, glues, cements and rare metals (particularly difficult to find and mine) is needed.

Lithium, nickel, cobalt and manganese are metals well used to produce battery electrodes. In order to produce 1 ton of lithium in Salar de Acatama in Chile, one of the major production centers in the world, 2000 tons of water are consumed, and this means that 65% of the water in that region is dried up.

The extraction of those materials damages the environment, has strong social consequences and is very energy intensive. Due to the ecological transition we are experiencing, the supply of those metals is necessary and extremely strategic to ensure an effective decarbonization of the transport sector.

European countries, for example, have no reserves of those metals available in their territory. Therefore, they plan to meet the future demand recycling and reusing EoL batteries.

 

RECYCLING TECHNIQUES AND RELATED CRITICAL ISSUES

Currently, two different techniques are used to recycle batteries: pyrometallurgy and hydrometallurgy.

In the first one, accumulators are melted in furnaces at temperatures over 1000 °C, producing a metal alloy, slag and gases. Then, the slag can be utilised in other industrial processes (such as the production of cement) and the alloy separated in his components. This process is widely used because of the possibility of treating batteries and other metallic objects together.

Hydrometallurgy consists in making battery electrolytes, or the metal alloy produced with pyrometallurgy, react with specific chemical solutions to separate different metals. Products have such a purity rate that the recovery is allowed.

Both pyro and hydrometallurgy require special plants, specialised workforce, high costs and the production of polluting waste (chemical or climate-altering gases). Both pyro and hydrometallurgy require special plants, specialised workforce, high costs and the production of polluting waste (chemical or climate-altering gases). For this reason, and due to the fact that the average capacity of an Eol battery is 80% of the initial one, it is preferred, at this point, to reuse EoL batteries in other sectors.

 REASSEMBLY AND REUSE OF BATTERIES

There are already different models of EVs on the market, from sedans to sports cars. According to the requirements, factories adapt battery packs to the car and this means that the recycling operations have to adapt themselves according to the specific battery to be treated. Actually, that means it is impossible to standardize and automate the industrial recycling processes and make the operation cheap. That is the reason why the trend is not to recycle, but to reuse batteries at the end of their life, or disassemble them to exploit the different components in other areas.

In both cases, before the disposal, batteries are cleaned from a layer of material that is deposited on the electrodes following prolonged use (SEI = solid electrolyte interphase). That is possible through the adoption of either chemical solvents which, however, alter the composition of the electrodes, with the risk of compromising their functioning, or with laser pulses.

It has been demonstrated that such technique allows the cleaning of a “poisoned” electrode, considerably increasing the rate of charge transfer across the surface. The interaction between laser and matter depends on lots of parameters (wavelength of the beam, duration of the treatment, absorbance of the materials, …) and controlling them it is possible to renew all possible varieties of electrodes.

 

CONCLUSIONS

Supplying rare metals for battery electrode is such a crucial question for automotive that batteries EoL management can have significant effects, not only from the environmental point of view alone, but also for the automotive sector itself.

Actually, the recycling chain has critical points mainly due to the variety of batteries available in the market and of waste generated throughout the different processes. It is a shared opinion that the reuse of batteries is the most safe, easy, environmental friendly and economically sustainable strategy to implement.

 

FONTI

G.Harper, R.Sommerville, E.Kendrick, L.Driscoli, P.Slater, R.Stolkin, A.Walton, P.Christensen, O.Heldrich, S.Lambert, A.Abbott, K.Ryder, L.Gaines & P.Anderson: “Recycling lithium-ion batteries from electric vehicles”,Nature, 2019.

M.O.Ramoni, H.Zhang: “End-of-life issues and options for electric vehicle batteries”, Springer-Verlag Berlin Heidelberg 2013;

I.Morse: ”A dead battery dilemma”, Science 2021;

E.Woollacott: ”Electric cars: What will happen to all the dead batteries?”, BBC 2021;

 

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