This common substance could replace lithium in the batteries of the future

By: Sarah Raza

Sodium-ion batteries are emerging as a possible alternative.

After decades of lithium-ion batteries dominating the market, a new option has emerged: batteries made with sodium ions.

Scientists have been researching alternatives to lithium for years. Much of the world relies on this kind of battery, but the mining and processing of its materials can be harmful to workers, local communities and the environment.

Sodium has recently emerged as one of the more promising options, and experts say the material could be a cheaper and more environmentally friendly alternative to lithium.

In the past few years, sodium-ion battery production has increased in the United States. Last month, sodium-ion battery manufacturer Natron Energy announced it would open a “gigafactory” in North Carolina that would produce 24 gigawatts of batteries annually, enough energy to charge 24,000 electric vehicles.

But sodium-ion batteries are still early in their development compared with lithium-ion, and they have yet to hit the market on a massive scale.

“It’s unlikely sodium-ion could displace lithium-ion anytime soon,” said Keith Beers, polymer science and materials chemistry principal engineer at technical consultancy firm Exponent.

Here’s what to know about these batteries.

How sodium-ion batteries work

There are many types of sodium-ion batteries, but the ones that will be manufactured in North Carolina are produced in the same way as lithium-ion batteries, just with different ingredients. Instead of using expensive materials like lithium, nickel and cobalt, these will be made of sodium, iron and manganese.

In a battery, ions move between electrodes during a charging and discharging process to generate electricity, explains Alvaro Acosta, a senior director at the solar developer Lightsource bp. In a sodium-ion battery, sodium ions carry the charge, and the negative electrode is made up of common materials like iron, carbon and nitrogen. Natron’s batteries use iron and manganese for their negative electrodes.

The biggest limitation of sodium-ion batteries is their weight. Sodium weighs nearly three times as much as lithium, and it cannot store the same amount of energy. As a result, sodium-ion batteries tend to be larger.

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Jens Peters, an economics professor at the University of Alcalá in Madrid, said the energy density could be improved over time in sodium-ion batteries. But, he added, “what we found out so far in our assessments is that it is not a game changer.”

Are they more sustainable?

Sodium-ion batteries are touted to be the environmentally friendly alternative to their lithium-ion counterparts, thanks to their raw materials. Sodium, iron and manganese are all abundant elements on the planet, so they require less energy to extract and cost less.

“Everyone knows that lithium-ion batteries are the pulse of mobile phones, transportation,” said Yang-Kook Sun, professor of energy engineering at Hanyang University in Seoul. “The issue over lithium-ion batteries is that they use highly expensive materials like lithium, nickel and cobalt.”

The environmental and human costs of that extractive mining are also issues. And at the end of their life, batteries made with these materials can leach toxins into the environment if disposed of improperly.

Sodium-ion batteries also last longer than lithium-ion ones because they can withstand more charge cycles, said Wendell Brooks, co-CEO of Natron Energy.

“Our product can have millions of cycles,” said Brooks, “where lithium-ion would have three to five thousand cycles and wear out a lot faster.”

But not all sodium-ion batteries are built alike, Beers said, or perform the same. And if a sodium-ion battery were to use the heavy metals found in lithium-ion batteries, then the environmental impact would likely be similar.

Will they replace lithium?

Experts say that sodium-ion batteries have limited uses compared with their lithium-ion counterparts, which currently power much of the technology in our lives, from smartphones to power tools to solar power backup storage.

Their biggest selling point is their small size and energy density; they’re small enough to fit in a camera, and a larger battery in your electric car can hold enough charge to drive a few hundred miles.

Sodium-ion batteries aren’t the best fit for smartphones or electric vehicles, which need to store lots of energy.

However, one advantage is their low cost. And they could be a good candidate in situations where the size of the battery isn’t a concern, like energy storage. “When something is built out to support grid or backup storage, it doesn’t need to be very dense. It’s staying put,” Beers said.