A Novel Concept for High Performance Stretchable Li-Ion Microbattery
Authors: Djenizian Thierry 
Published: May 2020

Energy storage microsystems composed of thin-film devices (supercapacitors and batteries) have attracted attention to ensure autonomy of complex devices for wearable microelectronics. Recently, flexible systems have been investigated as deformation and integration of rigid micropower sources cannot be achieved.1-5 The technological challenge is to design energy storage devices showing high electrochemical performance with advanced mechanical properties to prevent crack issues during electrochemical and mechanical tests. But in simple flexible micropower sources, the strains experienced by the active materials during bending usually remain well below the typical levels required leading to multiple fractures and subsequent loss of electrical contact.
In this work,the fabrication of microstructured electrodes based on micropillars supported on serpentine interconnects have been achieved by laser patterning technique. Morphological and chemical characterizations confirm the formation of independent micropillars while preserving the underlying current collector. We show that unlike compact and continuous electrode thin-films, vertical micropillar structures supported on serpentines can be stretched up to 70% without structural damaging owing to the presence of empty spaces that can prevent the formation of cracks and the electrode delamination. The present approach based on the fabrication of microstructured electrodes supported on serpentine interconnects can be extended to a wide range of materials, which opens promising perspectives for the conception of truly stretchable devices such as stretchable micro-batteries.6

This innovative approach has been used to fabricate a flexible micro-battery for powering a smart contact lens7 and garments. The innovative micro battery approach relies on two flexible substrates assembling consisting of polydimethylsiloxane (PDMS) supporting 1 cm2 surface area disk of LNMO and LTO serpentine electrodes separated by a gel polymer electrolyte.
Interestingly, the micro battery shows in the first reversible cycle a charge and discharge areal capacities of 1.22 mAh·cm−2 and 1.196 mAh·cm−2, respectively. The coulombic efficiency for the first reversible cycle corresponds to 96.17%. Regarding the cycling performance, the LTO/ polymer/LNMO micro battery has been assessed at fast kinetics for 30 cycles. The micro battery delivers 73.5 µAh.cm-2 at 6C, 47 µAh·cm−2 at 12C and 32 µAh·cm−2 at 20C with a remarkable stability.

References
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