Microelectrode Studies of Lithium Battery Materials

Abstract

Personal electronic devices rely on regular replacement of primary batteries or recharging of secondary batteries, requiring users to carry backup batteries or be tied to docking stations. A more desirable solution would be the integration of micro or nanosystems including energy storage with energy harvesting and the microelectronic devices to be powered. The autonomy of such devices requires the development of novel storage solutions for the scavenged or harvested energy. A truly autonomous device would have an on-device energy storage system that: (1) interfaces with various energy harvesting components, (2) provides power on demand to the electronic sensing, communication, and display components, and (3) retains its performance on charge and discharge cycling over the anticipated device lifetime. In the typical 2D, thin-film geometry, lithium diffusion and poor electronic conductivity limits electrode thickness to micrometers and thus large surface areas resulting in a battery dominated by the substrate and other inactive cell components. Commercial thin film microbatteries are typically rated at <1 mWh/cm2. The target energy storage solution should occupy a volume no larger than the electronics it drives (sub <0.1 cm3) and be integrated on chip to store energy harvested at a level of 10 mW/cm2. Integrated electronic and energy devices for advanced micro and nanosystems technology therefore require energy sources with increased performance per unit substrate area. This requires not only structured electrodes to increase the surface area and quantitiy of active materials per unit footprint but materials with improved electronic characteristics for increased rate capabilities. In this work we will describe the results of core-shell lithium battery nanomaterials analysis at microelectrodes.