Making Fiber‐Shaped Ni//Bi Battery Simultaneously with High Energy Density, Power Density, and Safety

Abstract Fiber‐shaped batteries are widely explored for a variety of important fields such as wearable electronics, information technology, internet of things, and public health. However, it remains difficult to simultaneously achieve high energy density, power density, and safety, which has largely limited their promising applications. Here, a new type of fiber‐shaped Ni//Bi batteries with remarkable electrochemical performances is created from hierarchically 3D electrodes, where reduced graphene oxide sheets framed with Bi serve as the anode while reduced graphene oxide sheets wrapped with nickel oxide/nickel function as the cathode. The fiber‐shaped Ni//Bi batteries show high energy density of 43.35 Wh kg⁻¹ or 26.01 mWh cm⁻³ and high power density of 6600 W kg⁻¹ or 3.96 W cm⁻³ with 96% capacity retention after 10 000 cycles. They are also safe with the use of aqueous electrolyte and can be further woven into the next‐generation flexible textile‐type power system. This work provides a general and efficient strategy to develop high‐performance batteries by designing hierarchically structured electrodes.