Translating the electrochemical performance of large batteries into tiny power sources has been a long-standing technical challenge, limiting the ability of batteries to power tiny devices, microrobots, and implantable medical devices. Researchers at the University of Illinois at Urbana-Champaign have created a high-voltage microbattery (>9 V) with high energy and power density unmatched by any existing battery design.

Paul Braun, Professor of Materials Science and Engineering (Grainger Distinguished Chair in Engineering, Director of Materials Research Laboratory), Dr. Sungbong Kim (Postdoc, MatSE, currently Assistant Professor, Korea Military Academy, co-first author), and Arghya Patra (Graduate, MatSE, MRL , co-first author) recently published the paper “Serially integrated high-voltage and high-power miniature batteries” in Cell Reports Physical Science.

The team demonstrated hermetically sealed (tightly closed to prevent exposure to ambient air), durable, compact lithium cells with extremely low packing mass fractions in single-layer, double-layer, and triple-layer stack configurations with unprecedented operating voltages, High power density and energy density.

“We need powerful micro-batteries to unleash the full potential of micro-devices by improving electrode structures and coming up with innovative battery designs,” explains Braun. Volume and quality, while the electrode area is getting smaller and smaller. This causes the energy and power of the battery to drop dramatically.

In their uniquely robust microbattery design, the team developed novel packaging techniques that use the positive and negative terminal current collectors as part of the package itself (rather than separate entities). This allows for cells with compact volume (∼0.165 cm 3 ) and low encapsulation mass fraction (10.2%). Furthermore, they achieved a high operating voltage for the cells by vertically stacking the electrode cells in series (so the voltages of each cell sum).

Another way to improve these microbatteries is to use very dense electrodes to provide energy density. Almost 40% of the volume of a normal electrode is occupied by polymers and carbon additives (inactive materials). Braun’s team grew fully dense electrodes free of polymers and carbon additives by direct electrodeposition at moderate temperatures. These fully dense electrodes offer higher volumetric energy densities than commercial electrodes. Microbatteries in this study were fabricated using densely plated DirectPlate™ LiCoO electrodes manufactured by Xerion Advanced Battery Corporation (XABC, Dayton, Ohio), which was spun out of Braun’s research.

Patra mentioned, “To date, micro- and nanoscale electrode structures and battery designs have been limited to power-dense designs at the expense of porosity and volumetric energy density. Our work has succeeded in creating a miniature energy source that demonstrates high-power density and volumetric energy density.”

An important application area for these tiny batteries includes powering insect-sized microrobots to obtain valuable information during natural disasters, search-and-rescue missions, and hazardous environments inaccessible to humans. Co-author James Pikul, an assistant professor in Penn’s Department of Mechanical Engineering and Applied Mechanics, noted, “High voltages are important to reduce the electronic payloads that microrobots need to carry. 9 V can directly power the motors and reduce the power required to communicate with some actuators.” The energy loss associated with raising the voltage to hundreds or thousands of volts.

Novel design helps develop powerful microbatteries

Kim added, “Our work bridges knowledge gaps at the intersection of materials chemistry, unique material fabrication requirements for energy-dense planar microbattery configurations, and nanoscale microelectronics that require high-voltage on-board power supplies to drive microactuators and applied microelectronics.” Motor.”

Braun, a pioneer in the field of battery miniaturization, concludes, “Our current microbattery design is ideally suited for high-energy, high-power, high-voltage, single-discharge applications. The next step is to translate the design to an all-solid-state microbattery platform, which is essentially more Liquid batteries are safer batteries with higher energy density.”