High-voltage liquid electrolyte microbatteries composed of the serial unit cells defined by surface tension in planar fluidic layers

Abstract

We present a high-voltage liquid electrolyte microbattery composed of the serial unit cells defined by surface tension in a planar fluidic layer. Compared to the previous liquid electrolyte microbatteries for MEMS actuators, the present microbattery has advantages of low interconnection loss and short charging time due to liquid electrolyte isolation through surface tension on integrated electrical lines. The present microbattery also makes it possible to partially activate several cells by partial liquid electrolyte filling and isolation. The present microbattery consis ts of a micromolded PDMS fluidic layer and a Zn electroplated electric layer. There are three different surface tension valves in the fluidic layer: cell-front valve, outlet valve, and cell-end valve to achieve simultaneous liquid electrolyte isolation by sequential injection of liquid electrolyte and air. We design and fabricate four types of devices: C1, C10, C20, and C40 according to the numbers of serial unit cells: 1, 10, 20, and 40, respectively. In the experimental study, we characterize the pressure differences of three surface tension valves in the fluidic layer, and verify the voltage, power density and capacity of the microbattery. The measured pressure differences of the cell-front valve, the outlet valve, and the cell-end valve are 175.0±8.6Pa, 575.8±42.1Pa, and 1883.0±400.6Pa, respectively, at the 10μl/min DI water flow rate. We verify DI water has same contact angle, 110° of an electrolyte $(H_2SO_4[1.5M]: H_2O_2[18M]=1:10, volume ratio)$. Experimentally, the pressure differences of three surface tension valves are independent of the flow rate range of 5~500μl/min for all types of devices. The measured maximum voltages are the 1, 7.6, 9.1, 12.3V; the measured power densities are the 40, 160.9, 153.0, $111.8μW/㎠$, and the measured capacities are 6.12, 2.45, 1.12, $2.06μAh/㎠$ in C1, C10, C20, C40, respectively. Partially activated cells show maximum voltages of 0.98, 1.9, 3.2V for ...