Designing batteries for simpler recycling might avert a looming e-waste disaster

Designing batteries for easier recycling could avert a looming e-waste crisis

What happens to millions of them? Kristoferb / Wikipedia, CC BY-SA

Zheng Chen, University of California, San Diego and Darren H. S. Tan, University of California, San Diego

With concerns about the effects of climate change growing, many experts are calling for more electricity to be used as a substitute for fossil fuels. Thanks to advances in battery technology, the number of plug-in hybrid and electric vehicles on US roads is increasing. And energy suppliers generate a growing proportion of their electricity from renewable fuels, which are supported by large battery storage systems.

These trends, coupled with a growing number of battery operated phones, watches, laptops, portable devices, and other consumer technologies, make us ask: What happens to all of these batteries when they wear out?

Despite the overwhelming enthusiasm for cheaper, more powerful, and more energy-dense batteries, manufacturers have paid comparatively little attention to making these essential devices more sustainable. In the US, only about 5% of lithium-ion batteries – the technology of choice for electric vehicles and many high-tech products – are actually recycled. As sales of electric vehicles and technical devices continue to grow, it is unclear who should handle hazardous battery waste or how to do it.

As engineers working on developing advanced materials, including batteries, we feel it is important to think about these issues now. By creating ways for battery manufacturers to establish sustainable manufacturing processes between production and recycling that meet both consumer and environmental standards, the likelihood of a battery waste crisis can be reduced in the next decade. Used electric vehicle batteries can still power devices like street lights, but there is currently no need to reuse them. Recycling is expensive and technically complex.

Dangerous content

Batteries present more complex recycling and disposal challenges than metals, plastics and paper products because they contain many chemical components that are both toxic and difficult to separate.

Some types of widely used batteries – particularly lead-acid batteries in gasoline-powered cars – have relatively simple chemicals and designs that allow easy recycling. The usual non-rechargeable alkaline or water-based batteries that power devices such as flashlights and smoke detectors can be disposed of directly in landfills.

However, today's lithium-ion batteries are sophisticated and not designed to be recyclable. They contain dangerous chemicals, such as toxic lithium salts and transition metals, which are harmful to the environment and can end up in water sources. Used lithium batteries also contain embedded electrochemical energy – a small amount of charge left after they become unable to power devices – that can cause fire, explosion, or harm to those who handle it.

In addition, manufacturers have little economic incentive to change existing protocols to incorporate recycling-friendly designs. Recycling a lithium-ion battery today costs more than the recyclable materials it contains are worth.

As a result, the responsibility for handling battery waste often rests with third-party recycling companies – companies that make money collecting and processing recyclable materials. It is often cheaper for them to store batteries than to treat and recycle them.

Recycling technologies that can degrade batteries, such as pyrometallurgy or combustion, hydrometallurgy or acid leaching, are becoming more efficient and economical. However, the lack of proper battery recycling infrastructure creates barriers along the entire supply chain.

For example, used batteries are typically transported long distances to recycling centers by truck. Lithium batteries must be packaged and shipped in accordance with the U.S. Department of Transportation Class 9 Hazardous Materials Regulations. Using a model developed by Argonne National Laboratory, we estimate that this requirement increases transportation costs to over 50 times normal freight.

Safer and easier

While it will be difficult to incorporate recyclability into existing traditional lithium-ion battery manufacturing, it is important to develop sustainable solid-state battery practices, which is a next-generation technology expected to hit the market this decade.

A solid-state battery replaces the flammable organic liquid electrolyte in lithium-ion batteries with a non-flammable inorganic solid electrolyte. This allows the battery to operate over a much wider temperature range and greatly reduces the risk of fire or explosion. Our team of nano-engineers are working to incorporate simple recyclability into the development of next-generation solid-state batteries before those batteries hit the market.

Conceptually, recyclable batteries must be safe to handle and transport, easy to disassemble, inexpensive to manufacture and minimally harmful to the environment. After analyzing the options, we selected a combination of specific chemical processes for next-generation solid-state batteries to meet these requirements.

Our design strategy reduces the number of steps required to disassemble the battery and avoids the use of incineration or harmful chemicals such as acids or toxic organic solvents. Instead, only safe, inexpensive materials such as alcohol and water-based recycling techniques are used. This approach is scalable and environmentally friendly. It greatly simplifies conventional battery recycling processes and makes it safe to disassemble and handle the materials.

Diagram showing steps to recycle a solid-state battery.Diagram showing steps to recycle a solid-state battery.A proposed method of recycling solid state battery packs directly and harvesting their materials for reuse. Tan et al., 2020, CC BY

Compared to recycling lithium-ion batteries, recycling solid-state batteries is inherently safer because they are made entirely from non-flammable components. In addition, in our proposed design, the entire battery can be recycled directly without separating it into individual components. This feature significantly reduces the complexity and cost of recycling.

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Our design is a proof-of-concept technology developed on a laboratory scale. Ultimately, it is up to private companies and public institutions such as national laboratories or state waste disposal facilities to apply these recycling principles on an industrial scale.

Rules for battery recycling

Developing an easy-to-recycle battery is just one step. Many of the challenges associated with recycling batteries arise from the complex logistics involved in handling them. Establishing the facilities, regulations and procedures for collecting batteries is as important as developing better recycling technologies. China, South Korea and the European Union are already developing battery recycling systems and mandates.

A useful move would be for governments to require batteries to wear universal labels, similar to the internationally recognized standard labels for recycling plastics and metals. This could help educate consumers and waste collectors about how to handle different types of used batteries.

Markings can be in the form of an electronic label on battery labels with embedded information such as chemical type, age and manufacturer. The provision of this data would facilitate the automated sorting of large quantities of batteries in waste disposal facilities.

It is also important to improve international recycling policy enforcement. Most battery waste does not occur where the batteries were originally manufactured, making it difficult to hold manufacturers responsible for handling it.

Such an endeavor would require manufacturers and regulators to work together on newer, recyclable designs and better collection infrastructure. When we face these challenges now, we believe it is possible to prevent or reduce the harmful effects of battery waste in the future.

Zheng Chen, Assistant Professor of Engineering, University of California, San Diego; and Darren H. S. Tan, PhD student in Chemical Engineering, University of California, San Diego

This article is republished by The Conversation under a Creative Commons license. Read the original article.

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