Scientists at USC have developed a water-based organic battery that is long-lasting and built from cheap, eco-friendly components (no metals or toxic materials).

The new battery is intended for use in power plants, where it could make the energy grid more resilient and efficient by creating a large-scale means to store energy for use as needed.

“The batteries last for about 5,000 recharge cycles, giving them an estimated 15-year lifespan,” said Sri Narayan, professor of chemistry at the USC Dornsife College of Letters, Arts and Sciences and corresponding author of an open-access paper published online by the Journal of the Electrochemical Society.

“Lithium ion batteries degrade after around 1,000 cycles, and cost 10 times more to manufacture,” he said.

Narayan collaborated with Surya Prakash, Prakash, professor of chemistry and director of the USC Loker Hydrocarbon Research Institute, and other USC scientists.

“Such organic flow batteries will be game-changers for grid electrical energy storage in terms of simplicity, cost, reliability and sustainability,” said Prakash.

The batteries could pave the way for renewable energy sources to make up a greater share of the nation’s energy generation. Solar panels can only generate power when the sun’s shining, and wind turbines can only generate power when the wind blows. That inherent unreliability makes it difficult for power companies to rely on them to meet customer demand.

With batteries to store surplus energy and then dole it out as needed, that sporadic unreliability could cease to be such an issue, the researchers suggest.

Redox-flow design

The new battery is based on a redox-flow design — similar in design to a fuel cell, with two tanks of electroactive materials dissolved in water. The solutions are pumped into a cell containing a membrane between the two fluids with electrodes on either side, releasing energy.

The tanks of electroactive materials can be made as large as needed — increasing total amount of energy the system can store — or the central cell can be tweaked to release that energy faster or slower, altering the amount of power (energy released over time) that the system can generate.

The team’s breakthrough centered around the electroactive materials. While previous battery designs have used metals or toxic chemicals, Narayan and Prakash wanted to find an organic compound that could be dissolved in water.

Such a system would create a minimal impact on the environment, and would likely be cheap, they figured.

Through a combination of molecule design and trial-and-error, they found that certain naturally occurring quinones — oxidized organic compounds — fit the bill. Quinones are found in plants, fungi, bacteria, and some animals, and are involved in photosynthesis and cellular respiration.

“These are the types of molecules that nature uses for energy transfer,” Narayan said.

Carbon dioxide as a source of power

Currently, the quinones needed for the batteries are manufactured from naturally occurring hydrocarbons. In the future, the potential exists to derive them from carbon dioxide, Narayan said.

The team has filed several patents related to design of the battery, and next plans to build a larger-scale version.

This research was funded by the ARPA-E Open-FOA program, the University of Southern California, and the Loker Hydrocarbon Research Institute.

Abstract of Journal of the Electrochemical Society paper

We introduce a novel Organic Redox Flow Battery (ORBAT), for meeting the demanding requirements of cost, eco-friendliness, and durability for large-scale energy storage. ORBAT employs two different water-soluble organic redox couples on the positive and negative side of a flow battery. Redox couples such as quinones are particularly attractive for this application. No precious metal catalyst is needed because of the fast proton-coupled electron transfer processes. Furthermore, in acid media, the quinones exhibit good chemical stability. These properties render quinone-based redox couples very attractive for high-efficiency metal-free rechargeable batteries. We demonstrate the rechargeability of ORBAT with anthraquinone-2-sulfonic acid or anthraquinone-2,6-disulfonic acid on the negative side, and 1,2-dihydrobenzoquinone- 3,5-disulfonic acid on the positive side. The ORBAT cell uses a membrane-electrode assembly configuration similar to that used in polymer electrolyte fuel cells. Such a battery can be charged and discharged multiple times at high faradaic efficiency without any noticeable degradation of performance. We show that solubility and mass transport properties of the reactants and products are paramount to achieving high current densities and high efficiency. The ORBAT configuration presents a unique opportunity for developing an inexpensive and sustainable metal-free rechargeable battery for large-scale electrical energy storage.