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

Abstract

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 LiFePO4 (LFP)-based and negative pseudocapacitive niobium pentoxide (Nb2O5)-based electrodes onto flexible current collector-free polyimide foils, through laser-writing of a mixture of HAuCl4, 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) Nb2O5 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-LiFePO4 battery electrodes prepared with the optimized laser parameters. Nb2O5//LiFePO4 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 laser-writing procedure, thus paving the path towards the facile fabrication of micro-batteries at a large scale.

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

“…In this case, heavy metallic foils are not required, significantly reducing the weight of the battery. [250] In a very elegant way, Yadav et al address this issue, by assembling a flexible zinc-ion battery (ZIB) based on DLW-engineered current collectors followed by electrodeposition of active materials. [379,382] The team laser-scribed interdigitated electrodes on PI followed by the electrodeposition of vanadium oxide and zinc.…”

3D Printing Enables Customizable Batteries

“…Third, the output current and voltage of planar interdigital batteries can be easily amplified due to their potential for miniaturization and integration, suggesting a wide range of potential applications in wearable electronics. [56]…”

“…Second, they offer a high degree of design freedom, and the size/shape of the cells and the areal capacity of the electrodes can be easily regulated. Third, the output current and voltage of planar interdigital batteries can be easily amplified due to their potential for miniaturization and integration, suggesting a wide range of potential applications in wearable electronics [56] …”

The status and challenging perspectives of 3D-printed micro-batteries

“…18,19 Besides, considering the architectural aspect, traditional batteries prepared by the slurry-cast method are difficulty to t the aesthetic versatility and shape customizability of microelectronics. [20][21][22] Remarkably, MBs can address the aforementioned problems of shape diversity and tailored structures by virtue of various microfabrication methods, such as photolithography, 23,24 laser scribing, [25][26][27] electrodeposition, 28,29 screenprinting, 30,31 and 3D printing techniques. [32][33][34] Photolithography and laser scribing can achieve interdigital patterns on a substrate but suffer from low material utilization.…”