In This Issue
Spring Bridge on International Frontiers of Engineering
March 15, 2018 Volume 48 Issue 1

Lifecycles of Lithium-Ion Batteries: Understanding Impacts from Material Extraction to End of Life

Thursday, March 15, 2018

Author: Gabrielle G. Gaustad

Since lithium-ion batteries (LIBs) were introduced for commercial use decades ago, they have quickly become the most popular power source for a wide variety of products. Their comparatively high power and energy densities make them an excellent source of power for consumer electronic devices and mobile applications in particular, including laptops, cellphones, digital cameras, electronic readers, and portable power tools.

More recently, the demand for LIBs has increased significantly with their use in electric vehicles (EVs). This rapidly growing demand may bring sustainability challenges throughout the battery lifecycle, from supply risks for critical metals and minerals to end-of-life waste management concerns.

This article reviews the sustainability challenges of LIBs, with a focus on both resource constraints and end-of-life economic and environmental tradeoffs, specifically for secondary life and recycling.

Introduction

The rapid technology trajectory of lithium-based energy storage introduces a great deal of uncertainty in quantifying not only demand and supply but also environmental and economic impacts.

Table 1 

For one, commercial products come in a variety of sizes and shapes (their form factor), as shown in table 1. Most portable consumer electronics, like laptops, use an 18650 cylindrical cell, which refers to its 18 mm diameter and 65 mm length. A rectangular laptop battery typically contains 8–12 of these form factor batteries. Small applications use a button cell for its long lifespan and size. Most larger applications, including EVs, use either prismatic or pouch form factor batteries, which are more expensive to manufacture than cylindrical but typically have a higher energy density due to improved packing efficiency.

Table 2 

In addition, LIB cathodes have significantly divergent compositions; table 2 lists the five most common. Lithium cobalt oxide (LCO) is by far the most common type of LIB, but with EV production ramping up other chemistries may dominate in the near future. Many automotive batteries are a blend of the cathode types shown in table 2. It should be noted that there are -stoichiometrically different versions of lithium nickel manganese cobalt oxide (NMC). The one listed in table 2 is NMC-111, which has the same amount of nickel, manganese, and cobalt on a mole fraction basis; other variations in development commercially are NMC-622 and NMC-811. The type is important because the materials in the cathode significantly influence supply (Olivetti et al. 2017), economics (Sakti et al. 2015), and environmental impacts (Wang et al. 2014a).

Potential Resource Constraints

With the potential for widespread adoption of EVs, concerns about resource constraints in the LIB supply chain have emerged. Lithium, natural graphite, cobalt, nickel, and manganese are all critical, with little opportunity for material substitution. The need to import them from a select few locations may also be a problem—the lack of supply diversity introduces risks to both individual firms and national interests.

There is little concern about a scarcity of lithium as it has a high crustal abundance and is present in a variety of concentrated sources. It has two main production routes: (1) evaporation from brines to precipitate lithium carbonate and (2) mining from the ore spodumene (pegmatites) to produce lithium carbonate or lithium hydroxide. The challenge with lithium is in ramping up battery-grade production to meet the current aggressive targets of some countries and auto manufacturers to go “all-electric” within the next decade (Kushnir and -Sandén 2012; Olivetti et al. 2017).

Supply and demand vary for the other resources. Most graphite, which is used prevalently in anodes, is supplied by China, and this lack of supply diversity can create vulnerabilities to supply disruption (e.g., from sociopolitical issues, natural disasters, or changes in regulations; Yang et al. 2017). Manufactured graphite might be an option, although it is significantly more expensive than mined natural graphite (Robinson et al. 2017), but the high diversity of other graphite demand sectors will likely ensure the supply for LIBs (Olivetti et al. 2017).

Challenges in the supply of cobalt lie mainly in its status as a byproduct of copper and nickel mining: its availability is tightly linked to the supply and demand dynamics of its parent materials. Furthermore, the location of most of the cobalt supply chain in the Democratic Republic of the Congo poses potential sociopolitical risks for disruption. Short-term supply bottlenecks have caused massive price spikes in the past that were debilitating to manufacturers (e.g., civil unrest in the 1970s; Alonso et al. 2007). Transitions from cobalt to more nickel-heavy cathode chemistries like NMC-811 may help alleviate demand pressures for cobalt.

Both nickel and manganese enjoy diversity of supply and other major demand markets, so constraints in demand for their use in lithium-ion batteries do not seem probable (Olivetti et al. 2017).

End-of-Life Management

Lithium-ion batteries are generally significantly less toxic compared to lead-acid and nickel-cadmium batteries (Pistoia et al. 2001), but they are nonetheless associated with environmental impacts. These include resource depletion (Notter et al. 2010), energy waste, and risks of land and groundwater pollution leading to ecotoxicity and human health impacts (Kang 2012).

Concerns about these impacts have motivated a patchwork of domestic and international legislation. In the United States, for example, California and New York ban and impose fines for the deposit of lithium-ion batteries in landfills (Richa et al. 2017a). In the European Union, the Battery Directive provides recycling targets for LIBs although its effectiveness is difficult to quantify (Kierkegaard 2007). Battery directives in other countries often target the heavy metals contained in metal hydride batteries and do not include LIBs (e.g., Brazil; Espinosa et al. 2004).

Determining the appropriate end-of-life disposition of lithium ion batteries is complex given the many options available; these include reuse in the original application, cascaded use in other applications, remanufacturing or refurbishment, refunctionalization, recycling, and ultimately disposal (figure 1).

Figure 1 

The variety of disposition options combined with the rapid technology trajectory of LIBs (resulting in changing form factors) and dynamic cathode chemistries (e.g., listed in table 1) further complicate this determination.

Reuse, Remanufacturing, and Refurbishment

Restrictions limit the reuse of EV batteries, but cas-caded use, or use in another application, has some promise. The remaining life of EV batteries (often as high as 80 percent capacity because of the high-demand nature of automotive consumption) has inspired examination of secondary use applications such as stationary power and grid load leveling (Neubauer et al. 2012). Any reuse route will require some testing and processing to prepare end-of-life batteries for use in another application. During these processes, often called re-manufacturing or refurbishment, it is necessary to assess the functional properties of end-of-life LIBs and access information from  the embedded battery management systems (Foster et al. 2014; Standridge and Corneal 2014). Remanufacturing processes for LIBs likely also require some degree of disassembly to access and replace underperforming cells or modules.

Cascaded use can lower costs of the battery system (Cready et al. 2003; Heymans et al. 2014) and reduce environmental impacts of LIBs (Cicconi et al. 2012). For example, one study found that lifecycle cumulative energy demand could be reduced by 15 percent for LIBs when used for stationary storage under base case assumptions and up to 70 percent under optimistic scenarios when compared to lead-acid batteries (Richa et al. 2017b).

But despite environmental and economic savings, significant barriers to reuse remain. One challenge is to match supply to demand in terms of both volume and properties (e.g., remaining lifespan, past life C-rates, minimum energy density). Quality control and consistent sourcing are concerns for users of second-life batteries. And those who provide such batteries—namely automotive manufacturers (original equipment manufacturers, OEMs)—cite liability, corporate policy, and collection and distribution costs as barriers. Recent incidents (e.g., the Samsung Galaxy Note 7 cellphone, hoverboards) involving explosions and thermal runaway of LIBs have increased concerns about the safety of secondary use applications.

Refunctionalization

Between reuse and recycling, a step that maintains some of the energy input in battery-grade cathode and anode materials is refunctionalization, the treatment of active battery materials to reestablish the electrochemical performance that degraded during use. Such techniques have been demonstrated using a variety of technologies (Liu et al. 2016; Sa et al. 2015; Senc´anski et al. 2017; Zou et al. 2013).

Most of the techniques for refunctionalization involve some type of relithiation. For example, a method using lithium carbonate as a treatment for LMO cathode EV batteries has been demonstrated (Dunn et al. 2012). For LFP cathode batteries, it is possible to restore the original capacity of 150–155 mAh/g through chemical relithiation, a method that results in about half the embodied energy required to make the same cathode material from virgin inputs (Ganter et al. 2014).

Laser radiation techniques have also been shown to be successful in removing solielectrolyte interface layers, a key cause of performance degradation, thus providing other routes to refunctionalization by restoring capacity (Liu et al. 2016).

Recycling

When reuse or refunctionalization of active materials is not possible or economically favorable, recycling is a clear path to resource recovery for LIBs and is generally preferred over disposal. Studies have found resource savings (Dewulf et al. 2010) and also show that LIB recycling can greatly reduce environmental impacts of EVs (Gaines et al. 2011; Notter et al. 2010; Sullivan et al. 2011).

Recycling processes for LIBs need to find a balance between low-cost, high-throughput methods that have low yields of some of the metals and labor- and reagent-intensive approaches to maximize metal yields. Current recycling processes for other battery systems provide examples at both extremes.

Infrastructure and Methods

The well-developed infrastructure for lead-acid automotive battery recycling has been mainly motivated by toxicity and disposal concerns associated with lead as well as favorable economics. Lead-acid recycling is generally a high-throughput smelting process. In contrast, many nickel–metal hydride batteries need to be hand sorted for hydrometallurgical recycling, a very labor-intensive process (Gaines 2014). And disassembling large-scale EV batteries is complex, challenging, and potentially dangerous work (Dorella and Mansur 2007). Most of the recoverable value resides in the base metals in the cathode, increasing disassembly cost and time as this is the last portion of the battery taken apart.

Research into preprocessing has found that high-throughput methods used for other primary and secondary streams may have promise for economic recycling of LIBs (Al-Thyabat et al. 2013). Shredding and size-based separation could successfully segregate valuable metals like cobalt and copper into different size fractions (Wang et al. 2016). For example, for LCO bat-teries, cobalt content has been improved from 35 percent by weight in the metallic portion before prerecycling to 82 percent in the ultrafine (<0.5 mm) fraction and 68 percent in the fine (0.5–1 mm) fraction, and excluded in the larger pieces (>6 mm). Such segregation may increase yields in further processing steps. However, because of safety concerns LIBs may be a poor match for traditional preprocessing technologies.

Economic Considerations

The economic impetus for recycling LIBs is mainly in the recovery of cobalt, by far the most valuable metal in them. As batteries transition away from cobalt-based chemistries, the potential profits for LIB secondary processors will go down significantly, unless other commodities in the batteries have significant price spikes (Wang et al. 2014a).

Compared to other electronic wastes, significantly more volume of spent LIBs is required to ensure profitability (Wang et al. 2014b), meaning that collection costs may play a role. The result may be more centralized processing facilities for LIBs as opposed to the distributed type used for other electronic wastes. Only a handful of companies handle LIB collection in the United States (e.g., Call2Recycle) and they must typically ship the batteries quite far for processing because of a lack of infrastructure.

Recovery of Materials

Most successful extraction technologies are hydro-metallurgical in nature, requiring low temperatures and strong acids to leach out the metals of interest into metals, salts, or hydroxides. These leaching approaches have shown excellent yields at the lab scale (Chagnes and Pospiech 2013). Researchers are working to optimize extraction from more environmentally friendly organic acids as well (Li et al. 2010, 2013). Pyro-metallurgical routes, like that employed at the Umicore battery recycling facility in Belgium, use high temperatures to melt mixtures of batteries to recover cobalt, nickel, and copper, but the lithium and aluminum typically end up as a waste byproduct in the slag.

One of the biggest challenges, which affects both reuse and particularly recycling, is the diversity of lithium-ion batteries, which makes for a dynamic scrap stream that can be difficult to manage. Even among batteries with the same cathode chemistry and form factor, the metallic composition can vary dramatically by manufacturer (Wang et al. 2014a). As the amount of valuable metals is crucial in ensuring profitability for secondary processors, such variability can negatively impact recyclers.

Furthermore, lithium-ion batteries commingled with the lead-acid input stream can cause dangerous conditions during smelting. Although the lead-acid battery recycling industry has advocated for labelling, there are no LIB labelling standards, so at this point even the development of sorting and segregation technologies may not be able to improve the process.

Disposal

Disposal of LIBs in municipal solid waste is the least desirable option as it can cause sanitation truck and landfill fires (Foss-Smith 2010), soil contamination from the organic electrolyte (Shin et al. 2005), and groundwater pollution from landfill leachate (Kszos and Stewart 2003). It also excludes opportunities for resource and energy savings.

Outlook

Demand for lithium-ion batteries will continue to grow over the next decade, especially with greater use of electric vehicles, and the LIB waste stream will increase exponentially over the next two to three decades (Richa et al. 2014). In the near term, the rising demand will cause pressures on the supply systems for lithium, cobalt, and natural graphite, with lesser effects on manganese and nickel.

The pressures of supply and demand may help to incentivize secondary routes like reuse, remanufacturing, refunctionalization, and recycling. Reuse, remanufacturing, or recycling of LIBs at their end of life can distribute costs over multiple lifespans and reduce environmental impacts, but the reuse or recycling infrastructure will need to be responsive to the stream of diverse and continually changing materials.

To pave the way for reuse opportunities in grid storage, load leveling, and stationary energy storage, removal of barriers may require strategic intervention at the firm or policy level. As the economics improve, opportunities exist for firms to emerge to serve as matchmakers between the supply of end-of-life LIBs and cascaded use demand.

In addition, research and development opportunities are plentiful across a variety of disciplines. In battery R&D, manufacturing scale-up of new chemistries and cells is needed to reduce costs; next-generation chemistries and form factors are needed to increase energy density and lifespan; and basic science research is needed to improve safety and stability.

Improved waste management will depend on infrastructure that optimizes resource recovery and economics. Secondary processors will need to ensure profitability with a dynamic input stream of LIBs. Policy initiatives will be important to promote standardization and incentivize collection.

Acknowledgments

Thank you to my students, colleagues, and collaborators without whom this work would not be possible: Drs. Callie Babbitt, Elsa Olivetti, Kirti Richa, Xue Wang, Matthew Ganter, Chris Schauerman, Nenad Nenadic, Brian Landi, and others. Funding for work in this area was provided by the National Science Foundation, New York State Energy Research and Development Authority, and the New York State Pollution Prevention Institute.

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About the Author:Gabrielle Gaustad is an associate professor at the Golisano Institute for Sustainability at the Rochester Institute of Technology.