We are living in an incredibly shrinking world — a world in which we see electronics decrease in size at an almost unbelievable rate. Think about the size of computer memory, music players, and cell phones. Each and every year, the size of microchips get smaller, while their capacities and abilities continue to increase. One area which researchers have been trying to innovate upon, with not all that much success, is in the production of batteries. Battery sizes have not been keeping up with the decreasing size of other electronics, thus creating some perplexing issues for electronic manufacturers and engineers.
This may all be about to change though, thanks to researchers at at the University of Illinois at Urbana-Champaign. The research team, consisting of Hailong Ning, James H. Pikul, Runyu Zhang, Xuejiao Li, Sheng Xu, Junjie Wang, John A. Rogers, William P. King, and Paul V. Braun have discovered a way of 3D printing lithium-ion microbatteries which can actually be placed directly onto small chips.
The process is one which combines 3D holographic lithography with the more conventional 2D photolithography (a process similar to methods used to make printed circuit boards) to create mesostructured electrodes. All of the details of this research have been published in a paper titled “Holographic Patterning of High Performance on-chip 3D Lithium-ion Microbatteries,” appearing in Proceedings of the National Academy of Sciences.
“Due to the complexity of 3D electrodes, it is generally difficult to realize such batteries, let alone the possibility of on-chip integration and scaling,” explained Hailong Ning, a MatSE graduate student and first author of the article. “In this project, we developed an effective method to make high-performance 3D lithium-ion microbatteries using processes that are highly compatible with the fabrication of microelectronics. We utilized 3D holographic lithography to define the interior structure of electrodes and 2D photolithography to create the desired electrode shape. This work merges important concepts in fabrication, characterization, and modeling, showing that the energy and power of the microbattery are strongly related to the structural parameters of the electrodes such as size, shape, surface area, porosity, and tortuosity.”
For traditional microscale devices, power is supplied off-chip because of the extreme difficulties in miniaturizing the energy storage technology. These batteries, however, suddenly become extremely desirable for applications which include microscale wireless sensors, portable and implantable medical devices, autonomous micro electromechanical systems (MEMS)-based acutuators, and distributed monitors, among many other things.
“For many of the applications, high energy density, high power density (charge and/or discharge), or some combination of high energy and power densities is required, all characteristics which can be difficult to achieve in a microbattery due to size and footprint restrictions, and process compatibilities with the other steps required for device fabrication,” the report reads.
This process, which as mentioned above, uses both 3D holographic lithography and conventional photolithography to create the template for the battery which is then put through a further process in which the thin layers of active materials are grown onto the 3D current collectors through a process of electrodeposition. The result is a microbattery containing interdigitated microscaled electrodes with mesostructured pores, providing for superior energy densities and plenty of potential for practical use. These batteries are extremely scalable and compatible with both MEMS and CMOS processes.
“Micro-engineered battery architectures, combined with high energy material such as tin, offer exciting new battery features including high energy capacity and good cycle lives, which provide the ability to power practical devices,” explained William King, a professor of mechanical science and engineering, and a co-author of this paper.
The researchers were able to demonstrate these batteries in use when connected to an LED. Even though the microbattery in the demonstration only had a volume of 0.04 cubic mm and a capacity of just 0.83μAh, it was able to easily power the LED at least 200 separate times. Quite impressive for a battery of this size. The video below shows the full charge-discharge cycle.
This may very well be a major breakthrough in micro-electronics. Could we soon see electronics become even smaller than they are today? The possibility of shrinking down battery sizes could mean the ever-shrinking world of electronics may just get put into fast forward! What do you think? Discuss in the 3D printed microbattery forum thread on 3DPB.com.Illinois.edu | PNAS]