Skip to Content
MIT News magazine

Go with the Flow

“Cambridge crude” could yield better batteries

When you think of electric cars, you don’t usually imagine pulling in to a filling station, saying “Fill ‘er up!” and zipping out minutes later. But that could change within the next few years.

A radically new approach developed by researchers at MIT could provide a lightweight and inexpensive alternative to existing batteries for electric vehicles and the power grid. These batteries could even make “refueling” as quick and easy as pumping gas into a conventional car—only in this case, what’s pumped in would be a thick black goo. Alternatively, the whole battery pack could be rapidly swapped out.

The new battery relies on an innovative architecture called a semi-solid flow cell, in which the positive and negative electrodes, or cathodes and anodes, are composed of particles suspended in a carrier liquid to form a mixture that the researchers jokingly refer to as “Cambridge crude.” The positive and negative suspensions are stored in two tanks and pumped through two sets of pipes into a reaction chamber (or more specifically, a stack of chambers), where they are separated by a barrier, such as a thin, porous membrane.

The chemical reaction in the chambers is essentially the same as that in an ordinary lithium-ion battery. One key difference is that the flow battery’s system for storing energy is physically separate from its system for discharging the energy when needed. Its energy capacity—the amount of energy it can store—is determined by the size of the tanks; its power capacity, or the rate at which it can deliver its charge, is determined by the size of the reaction chamber.

The team set out to “reinvent the rechargeable battery,” says Yet-Ming Chiang ‘80, ScD ‘85, who developed the idea with a fellow professor of materials science, W. Craig Carter, and Mihai Duduta ‘10, graduate student Bryan Ho, and others.

The key insight was that it would be possible to combine the basic structure of a little-known and low-energy-density technology called aqueous-flow batteries, which use electrode material dissolved in a liquid electrolyte, with the proven high-energy-density chemistry of lithium-ion batteries. While dissolving a material changes its chemical behavior significantly, suspending bits of solid material preserves the characteristics of the solid, making it possible to take advantage of its high energy density. So the team pulverized the batteries’ solid materials into tiny particles, which can be carried in a liquid suspension that flows like quicksand.

The researchers believe that the technology could halve the size and the cost of a complete battery system, including its structural supports and connectors. Those savings could help make electric vehicles a compelling replacement for gas- or diesel-powered vehicles. A battery could be “refueled” two ways: by replacing the discharged liquid slurry (which would later get recharged at the filling station) or by simply plugging it in to an ordinary outlet to recharge.

The same basic system could work with many different electrode materials. “We’ll figure out what can be practically developed today,” Chiang says, “but as better materials come along, we can adapt them to this architecture.”

Keep Reading

Most Popular

individual aging affects covid outcomes concept
individual aging affects covid outcomes concept

Anti-aging drugs are being tested as a way to treat covid

Drugs that rejuvenate our immune systems and make us biologically younger could help protect us from the disease’s worst effects.

Europe's AI Act concept
Europe's AI Act concept

A quick guide to the most important AI law you’ve never heard of

The European Union is planning new legislation aimed at curbing the worst harms associated with artificial intelligence.

Uber Autonomous Vehicles parked in a lot
Uber Autonomous Vehicles parked in a lot

It will soon be easy for self-driving cars to hide in plain sight. We shouldn’t let them.

If they ever hit our roads for real, other drivers need to know exactly what they are.

crypto winter concept
crypto winter concept

Crypto is weathering a bitter storm. Some still hold on for dear life.

When a cryptocurrency’s value is theoretical, what happens if people quit believing?

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at with a list of newsletters you’d like to receive.