Electrospun carbon nanofibers functionalized with NiCo2S4 nanoparticles as lightweight, flexible and binder-free cathode for aqueous Ni-Zn batteries

Aqueous nickel-zinc (Ni-Zn) batteries hold great promise for large-scale energy storage systems. However, traditional Ni-based cathode electrodes are generally consist of none capacity contribution additives and heavy current collectors, resulting in a low percentage of the active materials. In this regard, developing lightweight, flexible and binder-free cathode electrodes for aqueous Ni-Zn batteries is highly desirable. Herein, for the first time, we develop a simple electrospinning technique to synthesize the one-dimensional (1D) electrospun carbon nanofibers functionalized with ternary NiCo2S4 nanoparticles (denoted as [email protected]2S4) as a lightweight, flexible and binder-free electrode for aqueous Ni-Zn batteries. Based on the self-standing [email protected]2S4 film as cathode, the as-fabricated aqueous [email protected]2S4//Zn battery exhibits a high capacity of 0.32 mAh cm−2 and 35.9 mAh cm−3 at a current density of 2 mA cm−2, and good rate performance (0.21 mAh cm−2 at 20 mA cm−2) and long-term cycling stability (83% capacity retention at 10 mA cm−2 after 2000 cycles). More importantly, a quasi-solid-state [email protected]2S4//Zn battery is also fabricated, which also displays an impressive energy density of 362.3 Wh kg−1, indicating the potential towards practical applications. Impressively, the volumetric energy density of [email protected]2S4//Zn battery are 58.2 mWh cm−3 (liquid) and 45.4 mWh cm−3 (quasi-solid-state), which are much larger than the values of other reported Ni-Zn batteries. Theses results indicate the self-standing [email protected]2S4 film is promising for for next generation electronic applications.