On-chip solid-state Zn-air microbattery and method for its manufacture

A microimprint method for on-chip fabrication of Zn-air microbatteries is presented, which bypasses complications of catalyst incorporation on the chip at a target position and paves the way towards production of miniaturized, rechargeable energy sources.

Challenge

On-chip microsystems are promising for intelligent electronics and may offer functions such as data communication, response to stimuli and sensing. However, integration limits are given either by mismatched form factors or insufficient energy densities of available batteries. Moreover, an environment-friendly operation and a high output energy are crucial criteria for the development of usable on-chip power supplies with long service times and high safety standards. Zn-air batteries (ZAB) are safe and have a significantly higher volume energy density in comparison to lithium ion and alkaline batteries. However, the fabrication of miniaturized, rechargeable ZAB stagnates, since the available techniques have drawbacks (e.g. use of liquid electrolyte and imprecise component positioning) and, hence, are incompatible with microfabrication processes.

Our Solution

Scientists from the University of Göttingen (Germany) have developed a novel method, which sets benchmarks for the fabrication of Zn-air microbatteries (μZAB) on a chip and bypasses the aforementioned limitations. Thereby, a Zn-anode is placed by electrodeposition or microlithography on the chip, followed by a semi-liquid hydrogel (comprised of a polymer and electrolyte). Upon treatment with electromagnetic irradiation (e.g. UV light), the semi-liquid hydrogel is transformed into a drop-free, yet sticky hydrogel and allows for a microimprint process to integrate the air cathode precisely at the targeted position during on-chip fabrication. On-chip integration of a bifunctional catalyst enables the μZAB to outperform a commercial Zn-air primary cell and exhibit a superior energy output and lifetime characteristics.

Fig. 1. On-chip incorporation of a μZAB with a microimprint design. Reprinted (adapted) with permission from H. Zhang et al., ACS Energy Lett. 2021, 6, 2491-2498. Copyright 2022 American Chemical Society.

Fig. 2. Practical performance and utility in electronic devices: a) schematic on-chip fabrication of a μZAB, b) μZAB powering a digital watch, c-e) performance of a μZAB and commercial ZAB. Reprinted (adapted) with permission from H. Zhang et al., ACS Energy Lett. 2021, 6, 2491-2498. Copyright 2022 American Chemical Society.

Advantages

Wireless charging, safe operation and excellent long-term cycling performance
Lifetime capacity twice longer compared to on-chip lithium ion microbatteries
Volume approx. 9 times smaller compared to a commercial, compact Zn-air battery
Three times more volumetric energy in comparison to a commercial Zn-air primary cell
Material/production supply of zinc is currently 100 times higher compared to lithium
UV light hardenable and free mouldable electrolyte, which allows fabrication without a tight/strong cover

Applications

Intelligent microsystems (e.g. microsensors, microactuators and microfluidics)
Mobile digitization and electronics (e.g. smart watches, smart phones, thin displays and tablets)
Microacustics (e.g. earbuds and hearing sensors)
Wearable functional devices (e.g. skin-mountable and health-monitoring electronics)
Internet of things (e.g. embedded computer systems, data exchange and communication networks)

Development Status

The manufacturing process and the function of the Zn-air microbattery have been successfully established.

Patent Status

International patent application: WO2022258762A1
European patent application: EP4352816A1
US patent application: US2024136617A1

Patent holder: Georg-August-University Göttingen public law foundation (Germany)

Refrences

H. Zhang et al. “On-Chip Integration of a Covalent Framework-Based Catalyst into a Miniaturized Zn-Air Battery with High Energy Density” ACS Energy Letters 2021, 6, 7, 2491-2498; Link to publication