Design, Fabrication and Testing of Silicon-integrated Li-ion Secondary Micro Batteries with Side-by-Side Electrodes

This paper reports the design, fabrication, and testing of silicon-integrated lithium ion secondary micro batteries with a side-by-side electrode setup. Two cavities separated by a narrow silicon spacer served as a containment for the electrodes and were etched into -Si by wet chemical etching using aqueous KOH solution. The etched silicon battery containment was passivated by a stress-compensated layer of SiO2/Si3N4. Ti/Pt-current collectors were applied by E-beam evaporation and lift-off structuring. A volumetric dispenser served to fill the cavities with slurries of the active materials – lithium cobalt oxide (LiCoO2) as the anode and graphite as the cathode material. Encapsulation, electrolyte filling, and electrochemical characterisation of the finished cells took place in an Ar-filled glove box. The fabricated batteries have shown a rate capability of up to 5C and a linear capacity loss rate of <1 % per cycle over 30 full-cycles. Battery containments with different cavity and spacer widths have been fabricated.