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The influence of the operating voltage range on the high-voltage charge/discharge characteristics of layered rock-salt positive electrode materials was investigated. The discharge capacity retention of LiNi1/3Co1/3Mn1/3O2 significantly improved as the discharge cutoff voltage (Vdc) increased. The polarization due to an increase in charge transfer resistance (Rct) was substantially increased by charge-discharge cycling of LiNi1/3Co1/3Mn1/3O2 with lower Vdc. In contrast, the increases in polarization and Rct were significantly suppressed when cycling with higher Vdc. The increase in Rct is caused by increased activation energy (Ea) of Li-ion transfer reaction at the electrode/electrolyte interface. An electrochemically inert Ni-O structure, which increases Ea and Rct, was observed at the surface of the LiNi1/3Co1/3Mn1/3O2 cycled with 2.5-4.6 V. The formation of the Ni-O structure was suppressed at the surface during cycling with 4.2-4.6 V. It was also confirmed that the observed dependence of the capacity retention, polarization, and Rct on the operating voltage range is basically common to LiCoO2 and LiNi0.81Co0.15Al0.04O2. The electrode/electrolyte interface with low Li-ion transfer resistance is stably retained when the charge/discharge voltage is limited to the high-voltage region only. [ABSTRACT FROM AUTHOR]

We have examined the local 3d electronic structures of Co-Au multinuclear complexes with the medicinal molecules D-penicillaminate (D-pen) [Co{Au(PPh3)(D-pen)}2]ClO4 and [Co3{Au3(tdme)(D-pen)3}2] by Co L2,3-edge soft X-ray absorption (XAS) spectroscopy, where PPh3 denotes triphenylphosphine and tdme stands for 1,1,1-tris[(diphenylphosphino) methyl]ethane. The Co L2,3-edge XAS spectra indicate the localized ionic 3d electronic states in both materials. The experimental spectra are well explained by spectral simulation for a localized Co ion under ligand fields with the full multiplet theory, which verifies that the ions are in the low-spin Co3+ state in the former compound and in the high-spin Co2+ state in the latter. [ABSTRACT FROM AUTHOR]

New sulfur-carbon composite positive electrode materials were synthesized through sulfurizing primary alcohols, and their electrochemical properties were examined. The sulfurized alcohol composites (SACs) showed relatively higher sulfur contents (more than 60 wt%) and were revealed to be an amorphous structure by high-resolution TEM observations. Raman and XAFS spectra showed the presence of S - S, C - S, and C - C bonds, and the C - C bonds mainly consisted of sp3 components, which makes a clear contrast to the previously reported organosulfur materials where the C - C bonds mainly consisted of sp2 components. The SAC positive electrode cells showed discharge capacities of more than 900 mAh·g-1 with relatively reduced cycle degradation. [ABSTRACT FROM AUTHOR]