The uses of batteries range greatly, but they generally serve to add convenience and utility to everyday lives. Batteries enable the portability of electronics, vehicle ignition without manual cranking, and even residential power storage for use with intermittent renewable energy sources. Perhaps most topically, batteries are the driving technology (pun intended) behind electric vehicles (EVs).

Since batteries are tied to EVs and renewable energy, they are often considered part of the sustainable energy picture. But how environmentally friendly are batteries? Case studies of lithium mining have shown that the process has damaging environmental impacts. For example, it can take approximately 500,000 gallons of water to extract one ton of lithium. Lithium-ion batteries also require toxic heavy metals such as cobalt and nickel. Extraction of these resources has significant environmental and ethical impacts.

If batteries are needed to enable sustainable technologies such as renewable energy and EVs, how can their drawbacks be mitigated? One answer is with recycling.

By recycling battery materials, the amount of raw material required to keep up with battery demand can be greatly reduced. Reduction in material demand would lead to less mining, and therefore lower environmental impact.

Unfortunately, battery recycling isn’t always straightforward. Though it is possible to recycle most batteries, there are some challenges. To better understand the recyclability of batteries, it’s helpful to understand the different types of batteries.

Types of batteries

Though batteries tend to be labeled as a single category, a wide variety of battery types exist. One of the main differentiations is primary versus secondary.

A primary battery is non-rechargeable. These include zinc, alkaline and non-rechargeable lithium-based batteries. Primary batteries are typically inexpensive and used for things like TV remotes, toys and inexpensive consumer electronics.

A secondary battery is rechargeable. Secondary batteries are typically lead-acid or lithium-ion-based. Secondary batteries can be found in items like cell phones, cars and laptops. These batteries are usually more expensive to purchase initially than primary batteries, but make up for the initial cost by avoiding the need to be replaced often.

Lead-acid batteries were once the most dominant type of secondary battery, making up around 50% of battery sales worldwide in 1999. These batteries are still used today in most combustion engine vehicles and also industrial energy storage. However, modern-day lithium-ion batteries have quickly risen in popularity, as they have significantly higher energy density and recharge rates than lead-acid batteries. The demand for lithium-ion batteries is projected to grow at a rate of over 14% per year.

While all battery types serve similar functions, the recycling process and efficiency can differ drastically. A study conducted by Battery Council International found that in 2017 lead-acid batteries had a recycling rate of 99.3%, making them the most recycled consumer product in the U.S. Since lithium-ion batteries are fairly new, it’s difficult to find exact figures on recycling rates, but some sources claim that only about 5% of lithium-ion batteries available for recycling actually get recycled.

Comparing the recycling process of lead-acid and lithium-ion batteries can help in understanding why such a wide discrepancy exists.

The lead-acid battery recycling process

Lead-acid battery types have been around for quite some time, and are typically relatively simple in their assembly. As such, the recycling of lead-acid batteries is a relatively simple process.

The typical recycling process for a lead-acid battery consists of the following steps:

• Step 1: The batteries are crushed in a hammer mill, and the battery acid is drained off and collected.
• Step 2: The battery pieces are transferred into a vat, where the heavy materials (such as lead) fall to the bottom and the plastic pieces rise to the top.
• Step 3: The plastic pieces are washed and sent to a plastic recycler.
• Step 4: The lead parts are cleaned and sent to a smelting furnace.
• Step 5: The battery acid (generally sulfuric acid) is either neutralized or converted to sodium sulfate (which can be used in other materials such as glass and textiles).

According to the World Health Organization, approximately 99% of lead-acid battery components are recovered in the recycling process.

The lithium-ion battery recycling process

Lithium-ion batteries are significantly more complex in both their design and recycling process than lead-acid batteries. One critical factor in processing lithium-ion batteries for recycling is safety. Lithium-ion Lithium-ion batteries, like those found in modern smartphones, can be recycled through complex processes.batteries can explode or burn if not properly discharged. Additionally, the complex assembly of the batteries may require several extraction processes to effectively recover the materials.

The recycling process for a lithium-ion battery will vary depending on the procedure chosen, but a typical process would involve the following initial steps:

• Step 1: Discharging of the battery.
• Step 2: Disassembly of the battery system.
• Step 3: Mechanical processing (such as shredding and crushing).

Following these initial steps, there are three potential methods for recycling the lithium battery components:

1) Direct recycling — This is the simplest method, in which the cathode or anode material are removed and reconditioned to be used in new lithium-ion batteries. Though it’s not always clear if the recycled material will work as well in the long-term as new material, this method has the advantage of low energy consumption and high recovery rate.

2) Pyrometallurgical processing — The first step of this method involves heating the disassembled cells to remove any electrolyte and plastic. Next, the temperature is increased into the “smelting reduction zone,” in which the remaining material is smelted into alloys of the target material. Though this process is relatively straightforward, it is significantly energy-intensive.

3) Hydrometallurgical processing — Hydrometallurgical processing uses various aqueous solutions to “leach” target materials into the solution. Once leached, the materials are recovered through precipitation reactions, generally controlled by adjusting the pH of the solution.

The above processes have a wide range of recovery effectiveness, spanning from 25% to 96%. Some of these processes may be utilized together to increase overall element recovery.

New recycling processes are currently in development. Some, such as the Li-Cycle technology, claim over 95% recovery rate for the elements in the lithium batteries.

Conclusion

Batteries have been a staple of everyday life for decades. New technological advancements such as renewable power, modern consumer electronics and EVs are causing a significant increase in battery demand worldwide.

While lithium-ion batteries are a key component in advancing sustainable technologies, the environmental impact of creating these batteries may actually work against a sustainable future. Mining techniques utilized to gather raw materials such as lithium, cobalt and nickel can cause significant environmental harm.

One way to mitigate these environmental concerns is with increased recycling of lithium-ion batteries. In its current state, lithium battery recycling is both complex and costly. Both technological advancements and government incentives may be required to fully realize the recycling potential of lithium batteries, and keep sustainable technology fully charged.

About the author

Brandon Curkan is a professional engineer and technical writer located in Alberta, Canada. Brandon received his BSc. in Mechanical Engineering from the University of Alberta in 2011, and is currently an engineering manager of a research group that conducts experimental programs for the energy industry. He creates technical content through his business at www.thecontentengineer.com