New Concept for a Gravity-Fed Flow Battery

When it comes to battery technology, there's always room for improvement. Researchers at MIT have taken a different approach to this field of research by going back to a design from the 1970s.

Liquid flow batteries have been around for quite a while in a design where positive and negative electrodes are each in liquid form and separated by a membrane; however, early versions were notoriously inefficient.

The liquid chemical slurry contained within gave the batteries a very low energy density, despite the total weight of the battery. In addition, battery systems were composed of a complex series of pumping systems, plumbing and the housing needed to contain the liquid.

This was improved more recently, using chemical compounds from conventional lithium (Li)-ion batteries.

An MIT research team has taken the improved Li-ion flow battery and found a new way to control that flow using a gravity-fed system similar in concept to an hourglass.

Kyocera Professor of Ceramics Yet-Ming Chiang, who worked on the project, stated that the concept is far from ready for production, but it does demonstrate some new ideas that could eventually lead to a technological breakthrough.

Building a Gravity-Fed Flow Battery

This new design removes the need for a pump and any plumbing by using a simple gravity-fed system. The liquid slurry that carries the electrodes can navigate between chambers, which enables a higher battery power density (how much energy it can deliver at a given moment) and energy density (how much total energy can be stored in the system).

This energy production rate can be adjusted by changing the battery’s angle and speed of flow. The battery concept here uses a hybrid liquid-and-solid chemical design to improve efficiency.

Chiang noted that the trickiest part was in controlling the characteristics of the liquid slurry to maintain the flow rates. The liquids are difficult to control once they start flowing—think of ketchup in a glass bottle. Because the rate of flow can be adjusted by changing the angle of the device, it can be set for maximum efficiency.

Being able to alter the battery’s power density and energy density could be useful in the case of intermittent power sources such as wind or solar, adjusting the battery’s capacity on the fly and allowing these sources to scale better while part of a grid-connected storage system. The materials in the new design are also considerably simpler and easy to produce than previous versions.

Future plans for the project include developing a fully liquid model, where both positive and negative electrodes are able to flow. Improving the system for delivery of liquid through the battery will help improve efficiency in large-scale applications going forward.