Bismuth-based metal-organic frameworks derived rod-like nanoreactors for neutral aqueous battery-type anode

Bismuth oxide (Bi 2 O 3 ) has received great attention as the promising battery-type anode due to its high theoretical capacity and wide operating voltage window, yet its slow reaction kinetics and poor cyclability are major obstacles affecting the performance of energy storage devices. Herein, by employing the bismuth-based metal-organic framework (MOF) CAU-17 as both the template and precursor, the Bi-Bi 2 O 3 nanoparticles encapsulated in carbon nanorods (Bi-Bi 2 O 3 @C NR ) are fabricated through pyrolysis combining deliberate oxidation-state modulation. The Bi-Bi 2 O 3 @C NR anode exhibits enhanced electrical conductivity, fast reaction kinetics, high specific capacity, and extended lifespan in sodium sulfate electrolyte. The robust, in situ derived carbon matrix as a rod-like nanoreactor and the introduction of metallic bismuth into the bismuth oxide crystalline structure enable the Bi-Bi 2 O 3 @C NR electrode to deliver a package of optimal electrochemical performance, as evidenced by substantial physicochemical characterizations, kinetics analysis and density functional theory calculations. Consequently, the neutral aqueous Na-ion battery-supercapacitor hybrid device based on the Bi-Bi 2 O 3 @C NR anode and δ-MnO 2 cathode can achieve high energy and power densities simultaneously with an ultra-wide potential window of 2.4 V. This work offers an opportunity to develop high-performance Bi 2 O 3 -based electrodes by designing kinetically favorable host structure with high stability and modulating oxidation states of the active component for the neutral aqueous battery-type anode.