Towards ultrahigh-energy-density flexible aqueous rechargeable Ni//Bi batteries: Free-standing hierarchical nanowire arrays core-shell heterostructures system

Fiber-shaped energy storage devices featuring characteristics of macroscopic one-dimension, light weight, super-flexibility, and weavability demonstrate promising prospects for a category of crucial fields such as portable and wearable electronics. Particularly, fiber-shaped aqueous rechargeable (FAR) Ni//Bi batteries can further promote the development of wearable electronics due to their characteristics of low cost, flat discharge plateau, and no dendrite growth. However, it is currently challenging to simultaneously achieve high energy and power densities, and safety, which has seriously restricted their promising applications. Herein, a new type of FAR Ni//Bi battery with extraordinary electrochemical performance is created from hierarchical core-shell heterostructured electrodes, where bismuth trioxide (Bi₂O₃) nanosheets (NSs) directly grown on the surface of titanium nitride (TiN) nanowire arrays (NWAs) act as the anode while nickel hydroxide (Ni(OH)₂) NSs anchored on zinc doping cobalt-nickel-oxide (Zn-CoNiO₂) NWAs surface act as the cathode. Our as-assembled FAR Ni//Bi battery demonstrates ultrahigh energy density of 314.96 mWh cm⁻³ and remarkable power density of 20.04 W cm⁻³ with 88.6% capacity retention after 5000 cycles, which significantly outperform most state-of-the-art FAR batteries. This study offers a comprehensive and efficient strategy to develop high-performance aqueous rechargeable batteries by designing hierarchical core-shell heterostructured electrodes.