Ionogel-Based Sodium Ion Micro-Batteries with 3D Na-Ion Diffusion Mechanism Enable Ultrahigh Rate Capability

The rapid development of microelectronics and microsystems has stimulated continuous evolution of high-performance and cost-effective micro-batteries. Despite of its competitiveness with huge application potential, sodium ion micro-batteries (NIMBs), are still underdeveloped. Herein, we demonstrate one prototype of quasi-solid-state planar ionogel-based NIMBs constructed by separator-free interdigital microelectrodes of sodium titanate anode and sodium vanadate phosphate cathode, both of which are embedded into three-dimensional interconnected graphene scaffold. Meanwhile, a novel NaBF4-based ionogel electrolyte with robust ionic conductivity of 8.1 mS/cm was used. Benefited from the synergetic merits from the planar architecture, dominated pseudocapacitance contribution, and 3D multi-directional Na-ion diffusion mechanism, the as-assembled NIMBs exhibit high volumetric capacity of 30.7 mAh/cm3 at 1 C, and high rate performance with 15.7 mAh/cm3 at 30 C at room temperature and 13.5 mAh/cm3 at 100 C at high temperature of 100 oC. Moreover, the quasi-solid-state NIMBs present outstanding flexibility, tunable voltage and capacity output, and remarkable areal energy density of 145 μWh/cm2 (55.6 mWh/cm3). Therefore, this work will provide numerous chances to construct planar NIMBs for microsystems.