NiO Flowerlike porous hollow nanostructures with an enhanced interfacial storage capability for battery-to-pseudocapacitor transition

As a lithium-ion battery (LIB) anode, transition metal oxide nanostructures usually exhibit an initially decreasing and subsequently increasing trend of specific discharge capacity, owing to the gradually enhanced interfacial storage capability. In this paper, a novel base-catalyzed reaction of nickel acetate is used to synthesize flowerlike hollow architectures of basic carbonate based precursor and then to obtain NiO flowerlike porous hollow nanostructures with a high surface-to-volume ratio. As a LIB anode at 200 mA g(-1), the observed discharge capacity of the working electrode decreases from an initial value of 1584.7 mAh g(-1) to the minimum value of 867.5 mAh g(-1) in the 76th cycle and then increases to the maximum value of 2142.8 mAh g(-1) in the 350th cycle. In each cycle, an interfacial fraction of the discharge capacity can be clearly distinguished and quantitatively estimated according to the discharging behaviors. These prove that the seemingly battery-to-pseudocapacitor transition relates both to bulk capacity loss and to interfacial capacity gain, depending upon the applied C-rate. Furthermore, the ordered arrangement of gradually crystallized Li2CO3, a main component of solid-electrolyte interface (SEI) layer, and its non-faradaic (double-layer capacitive) and faradaic (further reverse lithiation-delithiation) contributions may explain the over-compensating ability of interfacial storage. (C) 2016 Elsevier Ltd. All rights reserved.