A team of researchers at Virginia Tech University have developed a battery with energy density an order of magnitude higher than lithium-ion batteries, while being almost endlessly rechargeable and biodegradable as well – because it’s made of sugar.
The battery is an enzymatic biofuel fuel cell – a type of fuel cell that uses a catalyst to strip molecules from molecules of a fuel material. Instead of using platinum or nickel for catalysts, however, biofuel cells use the catalysts made from enzymes similar to those used to break down and digest food in the body.
Sugar is a good fuel material because it is energy dense, easy to obtain and transport, and so simple to biodegrade that almost anything biological can eat it.
Sugar-based fuel cells aren’t new, but existing designs use only a small number of enzymes that don’t oxidize the sugar completely, meaning the resulting battery can hold only small amounts of energy that it releases slowly.
A new design that uses 13 enzymes that can circulate freely to get better access to sugar molecules, however, is able to store energy at a density of 596 amp-hours per kilogram – an order of magnitude higher than lithium-ion batteries, according to Y.H. Percival Zhang, who studies biological systems engineering at the College of Agriculture and Life Sciences and College of Engineering at Virginia Tech.
“Sugar is a perfect energy storage compound in nature,” Zhang said in a statement announcing publication in Nature Communications of his paper describing the battery. “So it’s only logical that we try to harness this natural power in an environmentally friendly way to produce a battery.”
The team Zhang leads developed a synthetic enzymatic pathway to expose the enzymes to maltodextrin, a sugar derived from starch, in an air-rich environment that allows the sugar to be oxidized more completely.
The primary byproducts of the process are water and electricity. “We are releasing all electron charges stored in the sugar solution slowly step-by-step by using an enzyme cascade,” Zhang said.
The design is simple and stable enough, Zhang added, to be developed within about three years into a commercially manufacturable product that could replace batteries in laptops and mobile phones.
The sugar battery is rechargeable, but also refillable. Sugar can be added to it in the same way toner can be added to a printer.