Characterization of lithium-ion capacitors for low-power energy neutral wireless sensor networks

Sensor nodes in wireless sensor networks (WSNs) are often powered by energy harvesting devices used to extend the lifetime of the nodes and energy storage elements are fundamental to collect the exceeding power incoming from the ambient. The stored energy is then consumed to supply the sensor node when the ambient energy is scarce or insufficient to satisfy the current requests from the load. To date, the choice of the storage element is made between rechargeable batteries and electric double-layer capacitors (EDLC or supercapacitors), and many works in literature exploit hybrid storage architectures. In this paper we characterize an innovative technology available on the market, namely the lithium-ion capacitor (LIC). We show that this cutting edge technology combines the high cell voltage, the energy density and the low self-discharge of a lithium battery with the power density, the high capacity and long cycle life of a supercapacitor.