Recycling technologies for end-of-life lithium ion batteries (LIBs) are not keeping pace with the rapid rise of electric vehicles

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Recycling technologies for end-of-life lithium ion batteries (LIBs) are not keeping pace with the rapid rise of electric vehicles, storing up a potentially huge waste management problem for the future, according to a new study.

A review of lithium ion battery recycling led by the University of Birmingham suggests that, while electric vehicles (EVs) offer a solution for cutting pollution, governments and industry need to act now to develop a robust recycling infrastructure to meet future recycling need.

The study, carried out in collaboration with researchers at the universities of Newcastle and Leicester, is published today in the 150th anniversary issue of Nature.

Dr. Gavin Harper, Faraday Research Fellow at the University of Birmingham, is lead author on the paper. He said: “The recycling challenge is not straightforward: there is enormous variety in the chemistries, shapes and designs of lithium ion batteries used in EVs.

Individual cells are formed into modules, which are then assembled into battery packs.

To recycle these efficiently, they must be disassembled and the resulting waste streams separated.

As well as lithium, these batteries contain a number of other valuable metals, such as cobalt, nickel and manganese, and there is the potential to improve the processes which are currently used to recover these for reuse.”

The issue of LIB waste is already significant and is set to grow as demand for EVs increases. Based on the 1 million electric cars sold in 2017, researchers calculated that 250,000 tonnes or half a million cubic metres of unprocessed pack waste will result when these vehicles reach the end of their lives.

There is also an enormous opportunity for the UK. Analysis by the Faraday Institution—the UK’s independent institute for electrochemical energy storage research- points to the need for eight gigafactories in the UK by 2040 to service the demand for LIBs.

The UK will need to develop sources of supply for the critical materials required for these batteries and recycled material could play a important role.

Professor Andrew Abbott, of the University of Leicester and co-author on the paper, said: “Electrification of just 2 per cent of the current global car fleet would represent a line of cars that could stretch around the circumference of the Earth – some 140 million vehicles.

Landfill is clearly not an option for this amount of waste.

Finding ways to recycle EV batteries will not only avoid a huge burden on landfill, it will also help us secure the supply of critical materials, such as cobalt and lithium, that surely hold the key to a sustainable automotive industry.”

The study identifies a number of key challenges that engineers and policy-makers will need to address, including:

Identifying second use applications for end of life batteries
Developing rapid repair and recycling methods, particularly given that large-scale storage of electric batteries is potentially unsafe
Improving diagnostics of batteries, battery packs and battery cells, so the state of health of batteries can be accurately assessed prior to repurposing
Optimising battery designs for recycling to enable automated battery disassembly, safer than the current manual handling techniques
Designing new stabilisation processes that enable end-of-life batteries to be opened and separated, and developing techniques or processes to ensure that components are not contaminated during recycling.
“These batteries contain huge amounts of power and at the moment we are still relatively unprepared about how we deal with them when they reach the end of their life,” explains co-author Professor Paul Christensen, of Newcastle University, who is also working with a number of UK Fire and Rescue Services on developing protocols for dealing with lithium ion battery fires.

“One of the areas of research for this project is to look at automation and how we can safely and efficiently dismantle spent batteries and recover the valuable materials such as lithium and cobalt.

But there’s also a public safety issue that needs addressing as second-life EV batteries become more widely available. What we need is an urgent look at the whole lifecycle of the battery – from digging the materials out of the ground to disposing of them again at the end.”

Paul Anderson, Co-Director of the Birmingham Centre for Strategic Elements and Critical Materials, adds: “Meeting these challenges will require a large amount of ambition as well as a consistent approach to policy-making.

This is essential if we are to create solutions within the design process that will allow us to make a smooth and sustainable transition to electric vehicles.”


Introduction

Driven by the electric vehicle (EV) boom [1], which led to a 3-fold increase in the price of lithium [2] and a 4-fold increase in that of cobalt [3] between 2016 and 2018, reclaiming lithium, cobalt, manganese and nickel (along with other valued materials like copper, aluminum and graphite) from spent lithium ion batteries has lately become profitable. Perhaps not surprisingly, numerous new lithium battery recycling plants started operation across the world, and those existing are expanding capacity.

In about 2 years, the recycling of lithium batteries which still in 2016 was claimed in Europe to lack economic viability as “only 3% of the material mix in batteries is made of lithium” [4], became profitable and convenient.

Investments started to flow targeting opportunities not only for recycling but also for refurbishing and reusing retired EV lithium-ion batteries (LIBs) in energy storage systems. “Certain companies” reads a working document of the European Commission dated mid 2018, “have already begun investing in recycling of used EV batteries in Europe (e.g. in Belgium and in France). Some have teamed up with car manufacturers to collect and recycle batteries” [5].

Hence, as lately emphasized by Melin, a reputed consultant in lithium-ion battery life cycle, “when it is not rare to read about recycling rates of 3 or 5 per cent… 58 per cent will be recycled this year” [6].

The environmental and economic benefits of LIB recycling are significant. As the lithium-ion recycling industry consolidates and the demand for spent LIBs increases, the old practice for which small batteries used by portable electronic devices were hazardously stockpiled in generic materials recovery facilities causing fires due to thermal runaway from damaged or short circuited batteries [7], will become a thing of the past.

This trend, we argument in this study, will further evolve and eventually first generation LIB recycling processes will be replaced by green chemistry processes producing highly pure (“battery-grade”) lithium, cobalt and manganese compounds along with graphite, copper and aluminum.

Recycling, in general, relies on first generation recovery technologies in which a physical treatment to obtain different streams of raw materials is followed by a hydrometallurgical process (leaching and extraction) to extract metals [8].

Lithium-ion batteries, indeed, generally use a graphite anode and a cathode made of lithium metal oxides generally comprised of lithium-iron phosphate (LFP), lithium-nickel manganese cobalt (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium-manganese oxide (LMO), or lithium-titanate oxide (LTO). First generation LIBs mainly used in portable electronics used lithium-cobalt oxide (LCO) [9].

The battery cells are assembled in modules and modules further assembled in battery packs. The voltage from “power” batteries supplying current to the motor of electric passenger cars or buses, can respectively top 300 V or even exceed 600 V.

Offering an updated global perspective, this study provides a circular economy insight on lithium-ion battery reuse and recycling.

Main text

Technology and chemistry aspects

By weight percentage (g material/g battery), a typical lithium-ion battery comprises about: 7% Co, 7% Li (expressed as lithium carbonate equivalent, 1 g of lithium = 5.17 g LCE), 4% Ni, 5% Mn, 10% Cu, 15% Al, 16% graphite, and 36% other materials [10].

Besides so called “calendar ageing”, a lithium-ion battery becomes “spent” (reduced ability to store and deliver electricity) mainly because during the charge and discharge cycles taking place in the battery cells a solid product forms due to reaction of the lithiated anode with the alkyl carbonate comprising the electrolyte solution [11].

The resulting solid electrolyte interphase mainly consisting of stable (such as Li2CO3) and metastable components (polymers, ROCO2Li, (CH2OCO2Li)2, and ROLi prone to decompose exothermically at >90 °C, releasing flammable gases and oxygen) [7] progressively deposits on the anode surface forming a passivating film. This film limits the electrochemical reaction by making graphite sites inaccessible for Li+ to intercalate and thus leading to an increase in internal ohmic resistance.

A typical EV lithium ion battery pack has a useful first life of 200,000–250,000 km ​[12], even though increasingly adopted fast-charging at >50 kW reduces the battery pack duration since battery degradation rapidly accelerates with charging current [13].

When, the automotive battery pack loses 20% (15% for certain EV models) of its initial capacity it becomes unfit for traction as the lower capacity of battery affects acceleration, range and regeneration capabilities of the vehicle [14].

Second-life batteries

Besides the beneficial effect on the price of grid electricity due to the concomitant expansion of EVs utilization and renewable energy generation (particularly solar photovoltaics) ​[15], a second synergistic effect of battery electric vehicle on renewable electricity uptake lies in the possibility to reuse the batteries at the end of their automotive lifecycle for stationary energy storage, nicely fulfilling the key “refurbish, reuse, recycle” circular economy principle.

Compared to use in EVs, stationary applications demand lower current density from the battery pack. Hence, batteries retaining between 80-85% of their original capacity are collected. Battery modules found to have similar power and life are sorted out and re-assembled in new “repurposed” battery packs, ready for stationary usage ​[16], such as utility-scale grid, building and telecommunication tower storage.

A significant public demonstration of the ability of repurposed batteries to provide energy storage and grid services (regulation of the alternating current frequency in the grid) is the 3 MW (nominal power)/2.8 MWh (nominal capacity) energy storage system installed in 2018 at Amsterdam’s “Joahn Cruyff Arena”, (Fig. 1[17].

During events at the stadium, the demand for electricity lighting, powering broadcasting, information technology equipment, catering, and security services increases from a baseload of around 200 kW to more than 3000 kW, for the entire duration of the event [17].

The new energy storage system installed at Amsterdam’s Arena is comprised of 590 battery packs (340 new and 250 second-life batteries originating from EV 24 kWh battery packs whose original capacity is now slightly less than 20 kWh).

Directly supplied by the EV maker the second-life batteries are certified to last 10 years, namely the equivalent of batteries included in 148 used exemplars of the first generation world’s best selling EV [18].

The batteries are contained in 61 battery racks (Fig. 2). Four bi-directional inverters manage the energy flows from the 4,200 rooftop PV modules, from and to the grid, and from the batteries to the stadium loads and to the grid (we remind that the grid accepts and supplies only alternating current, whereas the PV modules and the batteries supply direct current only).

The new energy storage system enables optimal use of both solar PV and grid electricity retrieved at low cost from the grid during the night hours.

Now the PV energy generated during the day, rather than being fed into the grid and sold to the grid operator at low price, goes to charge the 2.8 MWh battery pack whose nominal capacity was chosen to meet the energy demand from the stadium loads for 1 h during the most important events with maximum power absorption; and for 3 h when accessory services such as catering are not in use [17].

Flattening (“shaving” in the jargon used by electricity practitioners) the peak demand with free PV or low cost grid electricity stored in the lithium batteries i) cuts the diesel fuel cost (fuel is used in generators whose use is made compulsory from football authorities), ii) avoids peak demand charges, and iii) generates a revenue stream when the energy storage system is used to provide well paid grid-balancing services, such as frequency control.

Similar energy storage systems combining second-life EV battery modules with battery and power management digital technology for both residential, commercial and industrial applications are increasingly commercialized across the world by a number of companies.

Similarly, in China the world’s biggest operator of telecommunication towers, since 2018 ended purchase of lead-acid batteries. All existing and rapidly ageing lead-acid batteries currently installed for back-up power at 98% of its 2 million telecom tower base stations (54 GWh battery storage demand) will be replaced by second-life LIBs [19]. Partnership agreements were signed with more than 16 EV and battery manufacturers, as second-life LIBs in 2018 were reported to be priced at less than $100/kWh, namely the same price of new lead-acid batteries [19].

For comparison, this translates into forthcoming demand for up to 2 million retired EV batteries only from China’s telecom base station back-up, since one single tower needs about 30 kWh back-up battery [19].

According to a thorough analysis conducted in 2017 by Melin, by 2025 about 75 per cent spent EV batteries will be reused in second-life solutions for several years after retirement from vehicles, after which they will be sent to recycling to recover all the valued components [20].

New green chemistry technologies

Reviewing first-generation metal recovery processes using pyrometallurgical or hydrometallurgical methods, scholars in China lately emphasized the need for new “selective leaching of most of the valuable metals from the spent LIBs” [8].

Discovered in 2015, one such green process for the recovery of metals from spent Li-ion batteries makes use of citric acid (H3Cit) and aqueous H2O2 affording Co and Li in excellent recovery yields (98% Co and 99% Li) [21].

In detail, the spent batteries are first discharged and then manually dismantled to recover the Al and Cu foils in metallic form and the separator, directly recycled after dismantling (Fig. 3).

Fig. 3

Fig. 3
Simplified pretreatment process of spent LIBs based on citric aicd/hydrogen peroxide oxidative leaching of Co and Li: (A) manual dismantling; (B) peeling off Al/Cu foils and recycling of Al and Cu (top); and circulatory leaching experiments under the optimized conditions using citric acid and H2O2 (bottom). [Reproduced with permission from Ref.21, Copyright American Chemical Society].

The waste cathode materials ground into finer fractions for the subsequent extraction process is obtained by calcining at 700 °C for 2 h the cathode materials to remove carbon.

The powder of cathode material thereby obtained is used as raw material for the leaching process under optimized and mild extraction conditions (80 min, 70 °C, 2.0 M H2O2, with reductant dosage of 0.6 wt%, and slurry density of 50 g/L).

Aqueous H2O2 acts as clean reductant during metal leaching (Eq. 1), with both metal ions and waste citric acid being simultaneously recovered by selective precipitation (unbalanced).H3Cit + LiCoO2 + H2O2→ Co3(Cit)2 + Co(HCit) + Co(H2Cit)2 + Li3Cit + Li2(HCit) + Li(H2Cit) + H2O + O2(1)

Co and Li ions dissolved in the lixivium are treated with oxalic acid and phosphoric acid solutions to recover Co and Li. The total reaction equation (Eq. 2) shows that water and oxygen are the only byproducts in the whole recovery process (unbalanced).LiCoO2 + H2O2 + H2C2O4 + H3PO4→ Co(C2O4)2 + Li3(PO)4 + H2O + O2(2)

In a truly closed-loop route typical of the circular economy, about 99% Co and 93% Li could be recovered as CoC2O4·2H2O and Li3PO4, respectively, whereas the recycled citric acid shows similar leaching capability as fresh acid (Fig. 3, bottom).

LFP batteries, we have discussed elsewhere ​[1], will remain for many years the dominating lithium battery technology used by electric vehicles. It is therefore particularly relevant the recent discovery of a green and economically viable process for recycling entire spent LiFePO4 batteries to battery grade (99 wt%) Li2CO3 ready for manufacturing new LFP batteries [22].

The process is based on the selective leaching of lithium based on oxidation of LiFePO4 to FePO4 with aqueous sodium persulfate (Na2S2O8), forcing lithium deintercalating from the cathode (Eq. 3), while neither Fe (0.048% leaching) nor P (0.387%) leach out from the cathode structure whose olivine crystal structure is fully retained during the lithium leaching process.2LiFePO4 + Na2S2O8 → 2FePO4 ↓ + Li2SO4 + Na2SO4(3)

In detail (Fig. 4), cathode scrap of LFP powder attached on Al foil obtained by a local battery recycling company is first separated from soft-package batteries via discharging and dismantling, and then cut into small pieces.

Fig. 4

Fig. 4
Flowsheet of the method for treating entire spent LiFePO4 batteries using aqueous sodium persulfate under neutral conditions for Li leaching. [Reproduced with permission from Ref.22, Copyright American Chemical Society].

More than 99% of Li is leached without the addition of acid and alkali under the optimal conditions of 1.05 times the stoichiometric amount of persulfate, under remarkably mild conditions (25 °C, 20 min stirring a 300 g L−1 suspension of powdered cathode plates) with nearly no wastewater and solid waste generation.

No prior separation of cathode active material and Al foil (the most demanding procedure in the present recycling process of spent LIBs) is required because in the strong oxidative environment, Al is passivated (formation of a thin layer of Al2O3) resulting in an extremely low leaching of Al.

The leaching of lithium is very rapid with >90% of Li leached into the solution in only 5 min, an further increases to 99.8% by prolonging the leaching time to 20 min. As a result, the most valuable element in spent LFP batteries is directly recovered as Li2CO3 of high purity (>99%) by simple addition of Na2CO3 to the leachate followed by evaporation.

In a closed-loop method with great potential for industrial upscale, the mother liquor obtained after evaporation is used to prepare valued Na2SO4·10H2O product via freeze crystallization, whereas the crystallized solution is returned to leach another batch of raw cathodes with the addition of fresh Na2S2O8.

Besides Li recovery, the process enables direct cathode recycling to make new LFP cathodes for new batteries using the well-crystallized orthorhombic FePO4 leaching residue whose XRD pattern is close to that of raw LiFePO4 cathodes (the reverse of the phase transformation occurring in the charging of LFP battery, in which LiFePO4 releases Li+ ion and turns into FePO4).

Affording highly pure (>99.5%) lithium carbonate, the aforementioned processes solve the main problem which so far has limited the industrial uptake of green chemistry processes in LIB recycling, namely the “lengthy processing and purification processes of the raw materials to reach battery grade” [23] which determines “the true cost to manufacture” [23] Li-ion batteries.

Practically useful research in the field of green chemistry recycling processes continues at fast pace.

Selected examples include the simultaneous recovery of Li and Co from LiCoO2 cathode materials in a single step with good leaching efficiency (97% for Li and 98% for Co) using 0.6 M tartaric acid as leaching agent and 3% (v/v) H2O2 as reducatant (30 min at 80 °C with a solid to liquid ratio of 30 mL/g) ​[24]; and the recovery of all valuable metals from LiNi0.5Co0.2Mn0.3O2 cathode with excellent leaching efficiency (100% for Li, 93.38% for Ni, 91.63% for Co, and 92.00% for Mn) using an environmentally friendly leachant mixture of 0.2 M phosphoric acid and 0.4 M citric acid [25].

In the latter case, acid consumption is low, and the extraction time short (30 min at 90 °C with a solid to liquid ratio of 20 g/L) with no need for reductant as citric acid acts both as leachant and reductant.

Economic aspects

In a recent patent [10], seven main components (cobalt, lithium, copper, graphite, nickel, aluminum, and manganese) were reported to comprise >90% of the economic value of a spent lithium-ion battery: Co (39%) and Li (16%, as LCE equivalent) followed by Cu (12%), graphite (10%), Ni (9%), Al (5%) and Mn (2%).

The economic (and environmental) advantages of EVs are so large and significant (electric buses, for example) [26] that, regardless of rapidly growing output from new large factories in China, the demand of Li-ion batteries currently overcomes supply. This is especially the case for countries and regions like Europe where limited Li-ion battery manufacturing takes place. One Germany’s bus manufacturer, for example, by early 2019 was reported to be unable to get the batteries needed to start manufacturing electric buses in 2020 [27].

New regulation in China now holds EV makers responsible for the recovery of batteries, requiring them to set up recycling channels and service outlets where old batteries can be collected, stored and transferred to recycling companies. By the end of February 2019, 393 carmakers, 44 scrapped car dismantling enterprises, 37 cascade utilization enterprises and 42 recycling enterprises had already joined the new traceability platform to track origin and owners of discarded batteries [28].

Furthermore, since 2017 new legislation forbids to import in China electronic waste, including batteries, which is leading China-based companies formerly supplying lithium carbonate, cobalt and nickel sulfates obtained from batteries retired from large consumer electronics manufacturers to establish new recycling plants “overseas” (in South Korea for example) ​[29]; as well as foreign EV battery makers to open recycling plants in China [30].

Industrial LIB recycling companies in China include Taisen Recycling, Zhejiang Huayou Cobalt, Brunp, Jinqiao Group, Jiangxi Ganfeng Lithium and GEM. The latter company, for example, operates in China 13 automated battery dismantling and recycling facilities where it manufactures the cathode precursors (Fig. 5), with an annual production capacity of cobalt, nickel materials of lithium ion batteries and cathode material exceeding 50,000 tons [31].

The products resulting from battery recycling are sold to battery manufacturers. Hence, it may not be surprising to learn that large battery manufacturers own recycling companies, as in the case of Brunp, a lithium-ion battery recycler in Hunan.

Though smaller, from Singapore (TES-AMM operating a plant using an hydrometallurgical process developed in France), through South Korea (SungEel) and Belgium (Umicore), from the U.S. and Canada (Retriev Technologies) through Australia (Envirostream Australia) and Great Britain (Belmont Trading), several other companies across the world operate LIB recycling facilities.

The list above is far from being exhaustive. What is relevant here is that, driven by dramatically growing uptake of LIBs for electric vehicles, recycling companies are rapidly expanding their facilities and new companies are entering the market. For instance, by early 2019 when the company recycled over 8,000 tons of retired batteries annually through an hydrometallurgical process, a Korean firm was undergoing a 5-fold expansion with three new plants due to start operations in Hungary, India, and in USA [32].

Market forecasts for the LIB recycling industry agree on significant growth, though forecasted figures vary. According to the aforementioned 2017 report ​[633], recycled lithium will reach 9 percent of total lithium battery supply in 2025 (namely 5,800 tonnes of recycled lithium, or 30,000 tonnes LCE), and that of cobalt almost 20 percent of the demand, with >66% lithium-ion batteries being recycled in China.

New green chemistry technology will further contribute to lower recycling costs. Amid the numerous green recovery processes, the battery recycling industry will uptake the cheapest and most versatile.

Indeed, upon developing the leaching process based on citric acid/phosphoric acid ​[25], Zhou and co-workers compared it with two other efficient and rapid metal recovery processes in leaching LiNixCoyMnzO2 cathode material, namely those using lactic [34] acid and hydrogen peroxide, and malic [35] acid and hydrogen peroxide.

The three processes have similar leaching temperature, solid to liquid ratio and leaching time. Assuming therefore to treat one ton of waste cathode materials, the difference in cost mainly stems from raw material prices, with the cost of the phosphoric acid/citric acid leaching process about 30% lower than the malic acid process, and approx. 38% lower than that using expensive lactic acid [25].

Low cost citric acid, indeed, is the single largest chemical obtained via biomass fermentation and the most widely employed organic acid [36].


More information: Recycling lithium-ion batteries from electric vehicles, Nature (2019). DOI: 10.1038/s41586-019-1682-5 , https://nature.com/articles/s41586-019-1682-5

Journal information: Nature
Provided by University of Birmingham

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