High-rate and ultra-stable Na-ion storage for Ni 3 S 2 nanoarrays via self-adaptive pseudocapacitance

Abstract Ni 3 S 2 nanoarrays directly growing on Ni foam are fabricated via an electrochemical corrosion method and used as freestanding electrode for sodium ion batteries. Based on high electronic conductivity facilitated by the 3D Ni backbone and fast surface redox reactions rendered by the ultrathin thickness of the Ni 3 S 2 nanoarrays, high pseudocapacitive contribution for the charge storage is induced in the Ni 3 S 2 -Ni electrode. Remarkably, the capacitive contribution is self-adaptively enhanced in cycling owing to the gradually reduced and stabilized charge transfer resistance, triggering exceptional electrochemical performance. The Ni 3 S 2 -Ni electrode delivers ultra-stable cycling with charge/discharge capacities of 344.2/350.6 mAh g −1 after 200 cycles at 150 mA g −1 as well as high capacity recovery of 427 mAh g −1 after 70 cycles from 150 to 3000 mA g −1 . Meanwhile, practical application for the Ni 3 S 2 -Ni electrode is also preliminarily assessed. It exhibits promising fast discharge/slow charge (750/150 mA g −1 ) performance with initial discharge/charge capacities of 285.4/275.7 mAh g −1 and 244.8/242.2 mAh g −1 after 300 cycles. When matching with Na 3 V 2 (PO 4 ) 3 cathode, it delivers discharge capacity of 347.8 mAh g −1 after 180 cycles at 200 mA g −1 .