Electrode, Electrolyte and Architecture Assessment for High Power Thin Film Microbatteries

Abstract

Silicon integrated on-chip energy storage is an attractive goal for hybrid power sources coupled with energy harvesting for ‘Internet of Things’ devices and applications. Typical thin film microbatteries are limited to low power and energy outputs in the 2D planar formats. One of the issues with solid-state thin film microbatteries is the high resistance of the electrolyte which can lead to significant potential drop when powering devices during sensor operation and communication. The ability to provide high currents in a small form factor is a critical need for the development of realistic long life devices. In this work we will describe the use of Comsol finite element simulations to assess electrode materials, appropriate electrolytes and optimised architectures for improved microbattery power outputs. The simulations were of a microbattery stack where non-porous additive-free LiCoO 2 is the cathode, lithium metal is the anode and solid-state, polymer, polymer-gel and liquid electrolytes were investigated. The simulations show the material utilisation and overall electrochemical cell behaviour of Li-ion electrode materials at typical and high power rates. Core-shell structures based on nanoarchitectures for electronic contact and active electrode materials have been investigated to improve power delivery for nanoscale active materials and for low conductivity oxide cathodes. The simulations indicate that the implementation of nanoarchitectures such as 3D and 3D core-shell nanoarchitectures when coupled with the appropriate electrolytes and interfacial reactions can have a significant advantage in terms of areal energy and power capabilities compared to a thin-film geometry for a microbattery cell. The deployment of these architectures for microbatteries where area is at a premium and high power capabilities are desirable should result in better performing hybrid energy and less complex power management systems. Acknowledgments The authors would like to acknowledge the financial support from Science Foundation Ireland (SFI) Grant number: 12/IP/1722, Nanomaterials design and fabrication for energy storage. This work is supported in part by a research grant from SFI co-funded by the European Regional Development Fund under Grant Number 13/RC/2077. This work is also supported in part by a research grant from the EU Horizon 2020 work programme – Enables, European Infrastructure Powering the Internet of Things, project number 730957.