Current Collector-Free Interdigitated Nb 2 O 5 //LiFePO 4 Micro-Batteries Prepared by a Simple Laser-Writing Process
Résumé
The recent development of the internet of things (IoT) raises new needs in energy storage micro-devices to power implantable and 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 such as electrochemical deposition, which does 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 about the integration of positive LiFePO 4 (LFP)-based and negative pseudocapacitive niobium pentoxide (Nb 2 O 5)-based electrodes onto flexible current collector-free polyimide foils, through laser-writing of a mixture of HAuCl 4 , cellulose acetate, and active material coated on polyimide. The influence of the laser energy during the laser-writing step on the electrochemical performance of the as-prepared electrodes was studied. Laser-scribed (LS) Nb 2 O 5 flexible electrodes exhibit a typical pseudocapacitive behavior, and deliver up to 114 μAh.cm −2 (205 mF.cm −2), while 76 μAh.cm −2 were recorded for LS-LiFePO 4 battery electrodes prepared with the optimized laser parameters. Nb 2 O 5 //LiFePO 4 micro-devices were assembled in a parallel-plate configuration, providing a 32 μAh.cm −2 areal capacity, despite the absence of any underlying current collectors. Finally, interdigitated planar micro-batteries were realized by this simple laserwriting procedure, thus paving the path towards the facile fabrication of micro-batteries at a large scale.
