Pacific Northwest National Laboratory (PNNL) materials scientist Ismael Rodríguez Pérez has formulated a new type of cell chemistry for zinc batteries to double the voltage of aqueous zinc batteries.
Until now, the use of graphite as a cathode has been limited by the narrow electrochemical stability of water, which caps out at 1.23 volts. To increase the performance, Pérez and his team gave the aqueous electrolyte an extra boost by using a highly concentrated ‘water-in-bisalt’ solution.
The solution widens the electrochemical stability window of the electrolyte and enables graphite as a cathode material in a practical aqueous system— something previously considered impossible. This helps stabilise the electrolyte at high voltages, allowing the graphite to electrochemically oxidise before the aqueous electrolyte.
The battery showed promising performance during testing. At approximately 2.3 to 2.5 volts, it achieved one of the highest operating potentials of any aqueous battery.
In partnership with colleagues from Argonne National Laboratory, US and the MEET Battery Research Center at the University of Münster in Germany, Pérez formulated a new type of cell chemistry for dual-ion batteries (DIB). The new DIB chemistry uses a zinc anode and a natural graphite cathode in an aqueous electrolyte.
Pérez is building on prior research conducted by Kang Xu from the United States Army Research Laboratory and Chunsheng Wang from the University of Maryland, who first developed these highly concentrated aqueous electrolytes in 2015.
Safer and more sustainable batteries
Cathodes made of highly abundant carbon-based materials, like natural graphite, are less costly and more sustainable than environmentally harmful, scarce, and expensive metals, like nickel and cobalt, which are regularly used in lithium-ion batteries. Using an aqueous electrolyte also makes DIBs safer as they are non-flammable compared to commercial lithium-ion batteries, which exclusively use non-aqueous electrolytes.
In DIBs, both the positive cathode and negative electrode can be made of low-cost carbon-based materials like graphite. This makes DIBs a particularly promising solution to support the widespread adoption of renewable energy sources, like wind and solar for the power grid.
Pérez said: “If we can achieve a high enough voltage for the battery, even if performance is not on par with lithium-ion batteries, we can make dual-ion batteries bigger and make them a suitable candidate for grid energy storage applications. Though you may not be able to use it to power your phone, your local utility can use it to store energy for your home, stabilise the grid, and increase reliability.”
Picture: Ismael Rodríguez Pérez formulated a new type of cell chemistry for dual-ion batteries called graphite||zinc metal aqueous dual ion battery (photo by Andrea Starr | Pacific Northwest National Laboratory)