Current Collector-Free Interdigitated Nb2O5 // LiFePO4 Micro-Batteries Prepared by a Simple Laser-Writing Process

Abstract

Abstract The recent development of the internet of things (IoT) raises new needs in energy storage micro-devices to power wearable applications. Conventional battery components, including electrode materials and current collectors, have to be miniaturized and integrated onto flexible substrates while keeping their electrochemical performance. Although numerous micro-fabrication processes were successfully adapted to prepare lithium-ion micro-batteries (Li-ion µBs), they often rely on wet processing routes which do not allow the preparation of energy micro-sources at a large scale. Laser-writing processes are among the most practical and versatile methods to deposit active materials as thin films on flexible substrates. Here, we report the integration of positive LiFePO4 (LFP)-based and negative niobium pentoxide (Nb2O5)-based electrodes onto flexible current collector-free polyimide foils through laser-writing. The influence of the laser energy on their electrochemical performance was studied, and optimized laser-scribed (LS) Nb2O5 (114 µAh.cm-2 / 205 mF.cm-2) and LS-LFP (76 µAh.cm-2) flexible electrodes were prepared. Asymmetric Nb2O5//LiFePO4 micro-devices were assembled in a parallel-plate configuration, providing 32 µAh.cm-2, despite the absence of any underlying current collectors. Finally, interdigitated planar asymmetric micro-batteries were realized by this simple laser-writing procedure, thus paving the path towards the facile fabrication of micro-batteries at a large scale.