RyoungHee Kim

Effects of Substrate Morphology and Postelectrodeposition on Structure of Cu Foam and Their Application for Li-Ion Batteries

bubbles are split into small bubbles by the nodules. In addition, the adhesive properties of the Cu foamdeposited on the nodular Cu foil are improved by the mechanical interlocking effects of the nodules. As a result of the postelec-trodeposition treatment, the mechanical strength of the Cu foam is significantly enhanced primarily due to the covering of thepost-Cu electrodeposit on the dendrite crystallites of the Cu foam. The Li capacity and cycle performances of a Sn anode areclearly improved when Sn is electrodeposited on the covered Cu foam on the nodular Cu foil compared with that on the uncoveredCu foam: 451 mAh g

Study on corrosion resistance of gas cylinder materials in HF, HCl and HBr environments

Abstract Corrosion properties of Mn steel, Cr–Mo steel and 316L stainless steel and effects of surface treatments including Cr or Ni coating, nitriding and oxynitriding on the corrosion resistance of steels were examined in halogen acid gas and solutions. Corrosion behaviours were evaluated by the potentiodynamic polarisation tests in 0·001M HF, HCl and HBr solutions and the exposure test in HBr gas with 1·13 ppm H2O for 24 h. The surface morphology of the tested samples was examined by optical microscope and SEM and the composition of the corrosion product was analysed by EDS after exposure of the tested alloys to HBr gas. The corrosion resistance of Mn steel and Cr–Mo steel were very poor but was considerably improved by Cr or Ni coating. Oxynitriding also reduced the corrosion rate while nitriding was not effective. However the corrosion resistance of steels with Cr, Ni plating or oxynitriding was still much inferior to electropolished 316L stainless steel, which was practically not damaged by corrosion tests in aqueous solutions nor in gas.

Microstructure evolution of novel Sn islands prepared by electrodeposition as anode materials for lithium rechargeable batteries

Here, we describe the striking irreversible volume expansion of micron-sized Sn anodes for lithium rechargeable batteries during cycling with brand-new Sn islands that are prepared by electrodeposition on a Cu substrate. Exceptional changes in the internal as well as external microstructure of the electrodeposited Sn islands are demonstrated by ex situ morphological analyses. The cross sectional micrographs of the Sn islands prove the widespread formation of nano-voids within individual Sn islands after initial Li dealloying followed by their enrichment during the subsequent cycles. These widespread voids and the following dead volume formed inside the Sn islands induce irreversible volume expansion in the micron-sized Sn anodes, thereby deteriorating the cycling performance of the Sn anodes.