Sweetening the Deal: Sugar Solution Boosts Power Output and Durability of Flow Batteries

In a ground-breaking study from the Pacific Northwest National Laboratory (PNNL), researchers have remarkably improved the capacity and longevity of flow batteries – touted as promising solutions for sustainable, large-scale energy storage. By adding a simple sugar called β-cyclodextrin to the electrolyte in a flow battery, the team managed to increase the peak power output by an impressive 60%. Notably, the battery maintained nearly all of its capacity even after a year of continuous charge and discharge cycles.

Flow batteries are distinct from typical car or laptop batteries as they are versatile and ideally suitable for long-duration, scalable energy storage. As the world teeters towards renewable energy sources, grid-scale energy storage provided by flow batteries becomes increasingly crucial. The technology helps smooth out the intermittency of renewable energy supply intrinsic to wind, solar, and hydroelectric power, thereby creating more reliable power systems.

The traditional flow battery system comprises two different liquid electrolytes stored separately, which circulate on either side of an ion-selective membrane to create a current when energy is needed. One of the advantages of this system is the ability to “refuel” or recharge it by replacing depleted electrolytes with charged ones.

The PNNL researchers, working in conjunction with researchers from Yale, decided to dissolve the simple sugar β-cyclodextrin into the battery’s anolyte (one type of electrolyte). Initially intended to help dissolve more fluorenol (a type of organic compound) into the water-based electrolyte, the sugar brought unexpected benefits.

As the first instance of a catalyst speeding the electrochemical reaction in flow batteries while dissolved in solution (a process referred to as ‘homogeneous catalysis’), the β-cyclodextrin provided a unique boost. It accepts positively charged protons, creating balance with the negatively charged electrons moving across the cell membrane. This equilibrium accelerated the reaction rate, supercharging the power level of the battery by a whopping 60%.

Having optimized the power output, the focus then shifted to longevity. The durability testing phase involved year-long, continuous charging and discharging of the battery. They found after a year of usage that the battery had a negligible loss of capacity, demonstrating extraordinary longevity, which is already typically longer than lithium batteries.

PNNL researchers have applied for patents and are exploring other similar compounds to potentially create a more efficient system. The solution offers hope for more sustainable energy storage by utilizing abundant and easily synthesized compounds, thus decreasing reliance on limited and potentially toxic materials.

This development forms part of a broader program within PNNL designed to tackle grid-scale energy storage issues and will be greatly bolstered by the upcoming launch of PNNL’s Grid Storage Launchpad in 2024. Notably, this represents the first recorded instance of a flow battery showing such durability in laboratory conditions, paving the way for transforming our energy storage capabilities globally.

The research Proton-regulated alcohol oxidation for high-capacity ketone-based flow battery anolyte was published in the journal Joule.