Electrodes are the veins of batteries, responsible for harnessing and transporting the lifeblood of energy storage devices: electricity. Battery power and efficiency largely hinge on the performance of these electrodes - and now a team led by researchers at Penn State has created a new design that holds promise for practical applications like mobile electronics and electric vehicles.
The team recently developed dense, thick electrodes with substantially improved cell-level charge capacity, while also enhancing mechanical strength to withstand degradation during repeated battery charge cycles. By using a novel manufacturing process that increases electrode performance, the team overcame the drawbacks typically associated with increasing an electrode's density and thickness.
The research was published today (Oct. 29) in Nature Communications.
According to Hongtao Sun, assistant professor of industrial and manufacturing engineering (IME) and principal investigator on the project, the key to improving batteries is increasing the amount of active material - the component that stores energy and impacts battery performance - in the electrodes.
"Traditionally, active material makes up only 30% to 50% of commercial battery cells," Sun said. "By simply making the electrode thicker, we can increase the overall amount of active material and boost the total energy of the battery."
Sun, who holds additional affiliations in biomedical engineering, material science and engineering, and the Materials Research Institute at Penn State, explained that increasing electrode thickness typically requires making the structure highly porous - more than 40% empty space - to allow charges to easily move around. However, that extra porosity reduces how much active material and, in turn, energy the battery can store overall. Although packing the electrodes more densely seems like an obvious solution to increase power, Sun explained how the compacted structure restricts charge transport, weakening the battery's performance.
To overcome this trade-off, Sun's team designed synthetic boundaries within its electrodes, which act as a "reservoir" for charges and allows for quick travel across the system. Using these boundaries, the electrodes can be made five to 10 times thicker and twice as dense as conventional electrodes, significantly increasing energy density within a limited volume. The resulting batteries demonstrated a potential energy density exceeding 500 watt-hours per kilogram at the cell level, a power level that could enable electric vehicles to achieve a much longer driving range per charge, according to Sun.
Sun said this strategy achieves an optimal balance between weight, thickness, volume and capacity, producing cell-level performance that exceeds today's commercial electrodes.
