Multiscale 3D hybrid carbon microelectrodes with candle soot and reduced GO nanoparticles as binder-free anode: An approach beyond 3D for high rate & high performance Li-ion batteries

The full potential of electrodes for superior electrochemical performance in lithium-ion batteries (LIB) is beyond the limits of conventional planar electrodes with higher mass loadings. In this article, we report a unique way to fabricate a hierarchical hybrid 3D microelectrodes architecture with low mass loading (~1.3 mg/cm²) for more effective and efficient lithium charge transport in LIB. To fabricate such hierarchical 3D microelectrodes, first, 3D carbon microelectrodes are prepared on stainless steel (SS) wafer via the carbon-MEMS approach followed by drop-casting reduced graphene oxide (rGO) nanoflakes and candle soot carbon nanoparticles solution on these 3D microelectrodes. As-fabricated hierarchical 3D microelectrodes are then tested as an anode in LIB that enabled high current density operations with enhanced specific capacities. 3D carbon hierarchical microelectrodes based on rGO and candle soot carbon nanoparticles with SS substrate deliver high specific capacities of 560 and 462 mAhg⁻¹ at 250 mAg⁻¹ current density after 100 cycles, respectively. Post cycling analysis after 100 cycles confirms the structural integrity of the electrodes. Further, the finite element method is used to investigate and predict the time-dependent Li-ion gradient within the 3D microelectrodes that confirms much improved Li-ion diffusion kinetics over conventional flat electrodes.