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

This paper reports the design, fabrication, and testing of silicon-integrated lithium ion secondary micro batteries with a side-by-side electrode setup. Cavities separated by narrow silicon spacers served as containments for two interdigitally arranged electrodes and were etched into <110>-Si by wet chemical etching. The etched silicon battery containments were passivated by a layer of SiO_x/Si_xN_y. Al current collectors were applied by sputtering and back etching. A volumetric micro dispenser served to fill the cavities with slurries of the active materials - lithium cobalt manganese oxide (Li_y(Ni_1/2Co_1/5Mn_3/10)O₂) as the cathode and lithium titanate (Li₄Ti₅O₁₂) as the anode material. Filling with electrolyte, encapsulation, and electrochemical characterization of the finished cells took place in an Ar-filled glove box. The fabricated batteries with IDE show considerably lower impedances than cells with single side by side electrodes and are capable of constant current loads up to 10 C. A linear capacity loss rate of <0.1% per cycle was observed over 30 full cycles at 0.2C.