Kirkendall Growth and Ostwald Ripening Induced Hierarchical Morphology of Ni-Co LDH/MMoS _x (M = Co, Ni, and Zn) Heteronanostructures as Advanced Electrode Materials for Asymmetric Solid-State Supercapacitors

By changing the mixed metal sulfide composition, morphology tuning of an active electrode material can be possible, which can have a huge impact on its electrochemical performance. Here, effective morphology tuning of Ni-Co layered double hydroxide (LDH)/MMoS _x (M = Co, Ni, and Zn) heteronanostructures is demonstrated by varying the composition of MMoS _x . Taking advantage of the benefits associated with Kirkendall growth and Ostwald ripening, tunable morphologies were successfully achieved. Among the Ni-Co LDH/MMoS _x (M = Co, Ni, and Zn) heteronanostructures, a Ni-Co LDH/NiMoS _x core-shell structured electrode delivered a high specific capacity of 404 mAh g ^-1 at 3 mA cm ^-2 and an extraordinary cycling stability (after 10 000 cycles) of 93.2% at 50 mA cm ^-2 . In addition, an asymmetric supercapacitor (ASC) device coupled with Ni-Co LDH/NiMoS _x as the cathode and Fe ₂ O ₃ /reduced graphene oxide as the anode exhibited excellent cell capacity and extraordinary cycling stability. Moreover, the ASC device provided a very high specific energy of 72.6 Wh kg ^-1 at a specific power of 522.7 W kg ^-1 and maintained the specific power of 23.5 Wh kg ^-1 at 5357.6 W kg ^-1 , demonstrating its high applicability to energy storage devices.