The cathode-active materials, Li1＋yMxMn2-xO4 （M = Al, Co, Ni, Zn, y = 0.02, x = 0.02） powder, were synthesized by sol-gel method using LiOH, Mn（NO3）2 as the starting materials, citric acid as a carrier and Al（NO3）3·9H2O or Co（NO3）2·6H2O or Ni（NO3）2·6H2O or Zn（NO3）2·6H2O as dopants. The influence of different doping elements on the structural properties of the as-prepared samples was investigated by X-ray diffraction （XRD）, infrared （IR） spectroscopy and scanning electron microscopy （SEM）. X-ray diffraction patterns of the prepared samples were identified as the spinel structure with space group Fd3m. The grain size increases gradually as the sintering temperature rises and corresponding activation energies for the grain growth have been estimated using Arrhenius’ empirical relation.
The adsorption of O and N atoms on the Ni（311） surface was investigated by the 5-parameter Morse potential（5-MP） method in detail. For the O-Ni（311） system, there are three surface adsorption states and the fcc-3-fold site is metastable; the frequency of 75 meV[67 meV in high resolution electron energy loss spectroscopy（HREELS） experiment] is attributed to the vibration at the hcp-3-fold site. For the N-Ni（311） system, however, there are only two surface adsorption states（no surface adsorption state was calculated atfcc-3-fold site）. In addition, subsurface states were predicted and all critical characteristics were obtained for the two systems.
DIAO Zhao-yu ZHANG yan ZHANG Xue-na WANG Ze-xin WANG Zhong-ni
The adsorptions of nitrogen atoms on Ru（0001）, （1010） low index surfaces and （1120）, （1121） stepped surfaces were investigated by the five-parameter Morse potential（5-MP） method in details, Calculated results demonstrate that N atoms show a tendency to be adsorbed at threefold sites. No subsurface state was found for N atoms on Ru（1010） surface. There exist 6 stable adsorption sites for N atoms on Ru（1121） stepped surface which can be classified into 3 types： the on-surface adsorption state, the facet adsorption state and the subsurface state. Moreover, two new perpendicular vibrations at 97 and 98 meV are predicted. All calculated results are in good accord with HR-EELS experiments.
DIAO Zhao-yu YU Hai-yan WANG Zhong-ni ZHANG Xue-na WANG Ze-xin
