Hybrid super-capacitor / battery material could be built into the structure of all types of construction projects — from the siding and drywall of homes to the chassis of airplanes and electrc cars and the cases of smartphones. Researchers from Vanderbilt University’s Nanomaterials and Energy Devices Laboratory are now designing materials that combine the best aspects of super-capacitors and batteries into a single hybrid material suitable for making such device cases. While the material’s energy density is currently less than that of a lithium-ion battery, it makes up for density by the much bigger volume of a case — plus it eliminates the space needed for a battery.
Pint’s super-capacitors currently store 10x less energy than a lithium-ion battery, but make up for that in the volume of the structure they are a part of, plus they last 1,000x longer than a battery, making them suitable for mobile devices, automobiles, aircraft, homes, and more.
“I would also argue that in some cases, ‘total energy’ should be a metric that matters to us. 10x less energy stored over 1,000x as many discharge cycles, this means that 100x more energy is stored over the lifetime of the system. That means they are better suited for structural applications. It doesn’t make sense to develop materials to build a home, car chassis, or aerospace vehicle if you have to replace them every few years because they go dead.”
A load-bearing, multifunctional material with the simultaneous capability to store energy and withstand static and dynamic mechanical stresses is demonstrated. This is produced using ion-conducting polymers infiltrated into nanoporous silicon that is etched directly into bulk conductive silicon. This device platform maintains energy densities near 10 W h/kg with Coulombic efficiency of 98% under exposure to over 300 kPa tensile stresses and 80 g vibratory accelerations, along with excellent performance in other shear, compression, and impact tests. This demonstrates performance feasibility as a structurally integrated energy storage material broadly applicable across renewable energy systems, transportation systems, and mobile electronics, among others.
Westover’s wafers consist of electrodes made from silicon that have been chemically treated so they have nanoscale pores on their inner surfaces and then coated with a protective ultrathin graphene-like layer of carbon
Next an ultra-thin layer of carbon — akin to graphene — is deposited in the pores. A polymer film that holds charged ions like the electrolyte in a battery, is then sandwiched between the two wafer/electrodes where it oozes into the pores. After the polymer cools and solidifies, the whole dual-wafer structure becomes extremely stable and immune to delamination, according to Pint.
The resulting super-capacitor could be fully charged in minutes — instead of hours for a battery — and could withstand stresses and pressures up to 44 pounds-per-square-inch and vibrational accelerations over 80g. Although silicon was used to build the demonstration super-capacitors, the researchers are planning to extend their technique to load-bearing composite materials for more robust applications, from carbon composites embedded with nanotubes to lightweight porous metals such as aluminum.