No abstract

The lithiation reaction of ZnO as an anode in a lithium-ion battery (LIB) is unclear. The electrochemical behavior of ZnO was investigated inside a transmission electron microscope (TEM) by constructing a nano-LIB using an individual ZnO/graphene sheet as the electrode. The lithiation reaction of ZnO/graphene was monitored by simultaneous determination of the structure with high-resolution TEM, electron diffraction pattern and electron energy-loss spectroscopy. Two kinds of reaction modes were revealed in terms of different reaction rates. One was the violent reaction mode, in which one particle can evolve into an aggregate of many nanoparticles within the Li2O matrix in 1-2 min. The other was the peaceful evolution mode, in which each ZnO nanoparticle evolves into a core-shell particle with multi-domains constituted of Zn and LiZn nanograins. Abnormally large Zn nanocrystals grow quickly in the violent reaction mode, which can suppress the formation of LiZn and impair the reversible capacity. Our observations give direct evidence and important insights for the lithiation mechanism of metal oxide anodes in LIBs.

This article reports a facile preparation of NiO–graphene composite by the combination of a solution-based method and subsequent annealing. X-ray diffraction and electron microscopy reveals that the graphene nanosheets are uniformly wrapped by porous NiO nanosheets in the product. The composite shows highly improved electrochemical performance as anode for Li–ion batteries (LIBs). The NiO–graphene nanosheets deliver a first discharge capacity of 2169.6 mAh g–1 and remain a reversible capacity up to 704.8 mAh g–1 after 50 cycles at a current of 200 mA g–1 in half cells. Contrarily, the pristine NiO nanosheets show only a reversible capacity of 134 mA g–1 after 50 cycles. The NiO–graphene composite also exhibits ameliorative rate capacity of 402.6 mAh g–1 at the current of 1600 mA g–1. In particular, these novel nanostructured composites show exceptional capacity retention in the assembled NiO–graphene/LiNi1/3Mn1/3Co1/3O2 full cell at different current density. The enhanced electrochemical performances are ascribed to the stable sheet-on-sheet architectures and the synergistic effects between the conductive graphene and thin porous NiO nanosheets.

No abstract

No abstract