Ionogel-based sodium ion micro-batteries with a 3D Na-ion diffusion mechanism enable ultrahigh rate capability

Abstract

The rapid development of microelectronics and microsystems has stimulated the continuous evolution of high-performance and cost-effective micro-batteries. Despite their competitiveness with huge application potential, sodium ion micro-batteries (NIMBs) are still underdeveloped. Herein, we demonstrate one prototype of a quasi-solid-state planar ionogel-based NIMB constructed by separator-free interdigital microelectrodes of sodium titanate anode and sodium vanadate phosphate cathode, both of which are embedded into a three-dimensional interconnected graphene scaffold. Meanwhile, a novel NaBF₄-based ionogel electrolyte with robust ionic conductivity of 8.1 mS cm⁻¹ was used. Benefiting from the synergetic merits from the planar architecture, dominant pseudocapacitance contribution, and 3D multi-directional Na-ion diffusion mechanism, the as-assembled NIMBs exhibit high volumetric capacity of 30.7 mA h cm⁻³ at 1C, and high rate performance with 15.7 mA h cm⁻³ at 30C at room temperature and 13.5 mA h cm⁻³ at 100C at a high temperature of 100 °C. Moreover, the quasi-solid-state NIMBs present outstanding flexibility, tunable voltage and capacity output, and remarkable areal energy density of 145 μW h cm⁻² (55.6 mW h cm⁻³). Therefore, this work will provide numerous chances to construct planar NIMBs for microsystems.