Depiction of microrobots in a hazardous environment. Credit: Alex David Jerez Roman, Beckman institute, UIUCScientists led by a team from the University of Illinois Urbana-Champaign have developed a high-voltage, hermetically sealed microbattery that offers high-energy and high-power density, improving on existing battery design. As part of the drive towards wireless communication electronics and increasingly small electronics for microbots, wearable medical devices, distributed sensors, motors and actuators, the new design is based on durable, compact, lithium batteries with exceptionally low package mass and excellent operating voltages.
Transforming the electrochemical performance of large format batteries to microscale power sources remains a technological challenge, constraining their ability to power microscale devices. This means powerful tiny batteries are required, which in turn depend on better electrode architectures and battery design. With batteries getting ever smaller, their packaging also becomes important in terms of battery volume and mass, especially as the smaller electrode area reduces the energy and the power of batteries.
This new design, reported in Cell Reports Physical Science [Kim et al. Cell Rep. Phys. Sci. (2022) DOI: 10.1016/j.xcrp.2022.101205], involves new packaging technology based on the positive and negative terminal current collectors as part of the packaging itself and not as a separate entity. This allows the batteries to have compact volume andlow package mass, while vertically stacking of the electrode cells in series enables a high operating voltage. High voltage is key to reducing the electronic payload that microrobots have to carry, and to power motors and reduce the energy loss from boosting the voltage needed from some actuators.
The team improved their microbatteries by using extremely dense electrodes. As standard electrodes are nearly 40% by volume occupied by polymers and carbon additives and not active materials, with intermediate temperature direct electrodeposition electrodes were grown that are completely dense and have no polymer and carbon additives. These electrodes provide greater volumetric energy density than their commercial counterparts.
As co-first author Arghya Patra said: “To date, electrode architectures and cell designs at the micro-nano scale have been limited to power dense designs that came at the cost of porosity and volumetric energy density. Our work has been successful to create a microscale energy source that exhibits both high power density and volumetric energy density.”
Such microbatteries could find uses in powering microrobots to identify important information during search and rescue missions, natural disasters, and in environments where direct human access is not practical. The team now hope to translate their design to all solid-state microbattery platforms, helping to make batteries that are inherently safer and more energy dense than liquid-cell counterparts.
“To date, electrode architectures and cell designs at the micro-nano scale have been limited to power dense designs that came at the cost of porosity and volumetric energy density. Our work has been successful to create a microscale energy source that exhibits both high power density and volumetric energy density.”Arghya Patra