Transforming Industrial Waste to Power, Future of Energy Storage

The batteries powering our phones, devices, and cars rely heavily on metals like lithium and cobalt, which are extracted through intensive and environmentally harmful mining practices. As the demand for battery-based energy storage grows, finding alternatives to these metal-based solutions is essential for advancing the green energy transition, the Journal of the American Chemical Society reported.

Researchers at Northwestern University have achieved a breakthrough by converting an industrial waste product into a highly efficient energy storage material. This organic waste, known as triphenylphosphine oxide (TPPO), has been repurposed for use in redox flow batteries — a type of battery designed for large-scale energy storage. While redox flow batteries have been widely studied and developed, this marks the first time TPPO has been utilized, offering a promising step toward sustainable and scalable battery technology.

Thousands of tons of the well-known chemical byproduct are produced each year by many organic industrial synthesis processes — including the production of some vitamins, among other things — but it is rendered useless and must be carefully discarded following production.

In a paper, a “one-pot” reaction allows chemists to turn TPPO into a usable product with powerful potential to store energy, opening the door for viability of waste-derived organic redox flow batteries, a long-imagined battery type.

“Battery research has traditionally been dominated by engineers and materials scientists,” said Northwestern chemist and lead author Christian Malapit. “Synthetic chemists can contribute to the field by molecularly engineering an organic waste product into an energy-storing molecule. Our discovery showcases the potential of transforming waste compounds into valuable resources, offering a sustainable pathway for innovation in battery technology.”

Malapit is an assistant professor in the Department of Chemistry at Northwestern’s Weinberg College of Arts and Sciences.

A small part of the battery market at present, the market for redox flow batteries is expected to rise by 15% between 2023 and 2030 to reach a value of 700 million euros worldwide. Unlike lithium and other solid-state batteries which store energy in electrodes, redox flow batteries use a chemical reaction to pump energy back and forth between electrolytes, where their energy is stored. Though not as efficient at energy storage, redox flow batteries are thought to be much better solutions for energy storage at a grid scale.

“Not only can an organic molecule be used, but it can also achieve high-energy density — getting closer to its metal-based competitors — along with high stability,” said Emily Mahoney, a Ph.D. candidate in the Malapit lab and the paper’s first author. “These two parameters are traditionally challenging to optimize together, so being able to show this for a molecule that is waste-derived is particularly exciting.”

To achieve both energy density and stability, the team needed to identify a strategy that allowed electrons to pack tightly together in the solution without losing storage capacity over time. They looked to the past and found a paper from 1968 describing the electrochemistry of phosphine oxides and, according to Mahoney, “ran with it.”

Then, to evaluate the molecule’s resilience as a potential energy-storage agent, the team ran tests using static electrochemical charge and discharge experiments similar to the process of charging a battery, using the battery, and then charging it again, over and over. After 350 cycles, the battery maintained remarkable health, losing negligible capacity over time.

“This is the first instance of utilizing phosphine oxides — a functional group in organic chemistry — as the redox-active component in battery research,” Malapit said. “Traditionally, reduced phosphine oxides are highly unstable. Our molecular engineering approach addresses this instability, paving the way for their application in energy storage.”

In the meantime, the group hopes other researchers will pick up the charge and begin to work with TPPO to further optimize and improve its potential.

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