Designing Uniformly Layered FeTiO(3) Assemblies Consisting of Fine Nanoparticles Enabling High-Performance Quasi-Solid-State Sodium-Ion Capacitors

Sodium-ion capacitors (NICs) that have integrated the dual advantages of the high output of supercapacitors and the high energy density of batteries have stimulated growing attention for the next generation of practical electrochemical energy storage devices. The last years have seen the unprecedentedly rapid emergence of ilmenite materials, which present great promise in the realm of energy storage. However, NICs based on ilmenite materials have been scarcely researched so far. Instead, most of the current devices explored applied flammable liquid electrolytes, leading to a concern about unexpected leakage and potential safety problems. Herein, a quasi-solid-state NIC is constructed by employing the prepared uniformly layered FeTiO(3) assemblies consisting of fine nanoparticles as anode and sodium ion conducting gel polymer as electrolyte. The resulting device delivers a high-energy-high-power density (79.8 Wh kg(−1), 6,750 W kg(−1)), putting it among the state-of-the-art NICs. Furthermore, the assembled quasi-solid-state device also manifests long-term cycling stability over 2,000 cycles with a capacity retention ~80%. The uniformly layered FeTiO(3) has great potential in developing low-cost and high-performance electrodes for the next generation of sodium and other metal ions-based energy storage devices.