NASA's Marshall Space Flight Center has developed a solid-state ultracapacitor with a unique combination of high capacitance and battery-like discharge characteristics. The high capacitance in a solid-state form can enable a new type of ultracapacitor, and in combination with the ability to deliver sustained power like a battery, can perhaps enable an entirely new class of energy storage devices.
Test devices have demonstrated high capacitance, and uniquely, a discharge behavior that is more typical of a battery. Data show that these test devices discharge rapidly down to a certain voltage, and then discharge slowly like a battery. Hence, the term hybrid ultracapacitor is used to describe the technology.
The technology was developed as a result of efforts to replace range-safety batteries used to power the systems that destroy off-course space launch vehicles. Other commercial applications where ultracapacitors or batteries are used may benefit as well.
The technology is an extension of closely related solid-state ultracapacitor innovations by the same team of inventors. The primary distinction for this specific technology is the addition of co-dopants to affect the dielectric behavior of the barium titanate-based perovskite materials. These co-dopants include lanthanum and other rare earths as well as hydroxyl ions. The materials are processed at the nanoscale, and are subjected to carefully designed thermal treatments.
The presence of the hydroxyl ions has been shown to provide several orders of magnitude increase in the capacitance of the dielectric material. Additionally, these high capacitance values are obtained at relatively low voltages found in current consumer and industrial electronics.
The technology has demonstrated capacitance values of up to 1,000 mF per device at 1V for use as an ultracapacitor. Solid-state design is safe and highly robust compared to traditional liquid or gel electrolyte designs. Additionally, a membrane separator is not used. Devices can be reliably and repeatedly charged and discharged for many thousands of cycles with no degradation, unlike that of other types of rechargeable batteries.
The capacitors tested to date are simple, single-layer devices. Ultimately, a range of manufacturing methods is possible for making commercial devices. Features of the technology enable manufacturing via traditional thick-film processing methods widely used in the capacitor industry, or via advanced printing methods for state-of-the-art printed electronics. Future efforts will be made to advance the manufacturing and packaging processes to increase device energy density, including multilayer devices and packages.