Wednesday, 31 May 2017
Grand Ballroom (Hilton New Orleans Riverside)
Nanostructure transition metal oxides (MO-type M = Fe, Co, Ni, Cu, . . . ) with rock-salt structure are promising anode materials for lithium ion batteries. These types of materials can store two to three times the capacity of graphite anode (372 mAh g-1) which is the state-of-the-art technology. Here we focus on the growth of Nickel oxide (NiO) prepared by chemical vapor deposition (CVD) directly on current collectors and understanding of the origin of the excess capacity. The synthesis of the NiO nanoplates by CVD directly on the current collectors is ideal for studying the electrochemical properties because they are no interferences from additives. In addition, the direct growth of the materials onto current collectors provides faster mass and electron transport due to the improvement in conductivity across the interfaces and through the materials due to its nanosize. The microstructural characteristics of the as-prepared NiO nanoplates were examined by high resolution transmission electron microscopy which showed that they were arranged randomly on the current collector. Selected area electron diffraction showed that the NiO is polycrystalline with the face-centered cubic crystal structure. The X-ray photoelectron spectroscopy showed that the as-prepared materials are pure NiO. We studied the galvanostatic discharge-charge of the NiO electrode. During the first discharge process from 3.0 V to 0.1 V, a plateau at approximately 0.70 V followed by a gradual decrease to 0.1 V, is observed. This is due to the reduction of Ni2+ to Ni0 and the formation of Li containing organic and solid electrolyte interface (SEI). The first discharge corresponds to approximately 1100 mAh/g which is equivalent to 3 mol of Li per mol of NiO which is more than the expected capacity of according to the conversion reaction: NiIIO + Li0 +2e- ß à LiI2O + Ni0 (718 mAh/g). The excess capacity of the NiO nanoplates and the cyclic voltammetry will be discussed.