Characteristics of Li-ion micro batteries fully batch fabricated by micro-fluidic MEMS packaging

Abstract

A cost-effective and reliable technology allowing extreme miniaturization of batteries into glass chips and electronic packages has been developed, employing a dispense-print process for battery electrodes and liquid electrolyte. Lithium-ion micro-batteries (active area 6 × 8 mm2, 0.15–0.3 mAh) with interdigitated electrodes were fabricated, tested and finally compared with the traditional battery architecture of stacked electrodes. Commercial graphite and lithium titanate anode as well as layered nickel cathode materials were used. All the processes for the micro-battery fabrication were established during this work; in particular the micro fluidic electrolyte filling process that allows simultaneous electrolyte supply to all cells on a planar substrate. Electrode mass reproducibility was sufficient for adequate electrode balancing. Current capability similar to the conventional face-to-face electrode configuration was achieved with interdigital electrodes that can be fabricated much easily on a substrate level. The cells were successfully cycled; several 100 cycles can be achieved. Additional results of life-time characteristics and electrochemical impedance spectroscopy are presented as well. These rechargeable micro-batteries can be used for future extremely miniaturized electronic products.