Soft chemical synthesis and characterization of lithium nickel oxide electrode materials

Abstract

Soft chemistry was used to prepare ordered nanophase Li0.6NiO2 electrode materials by completing the oxidation of Ni2+ to Ni3+ and/or Ni4+ species with H2O2 oxidant during solution reactions at 50–60 °C and evaporation at 105–150 °C rather than during sintering. Both elemental analysis and electron spectroscopy for chemical analysis (ESCA) results indicate that oxidation was completed. The deconvoluted ESCA spectra of nickel ions exhibited a semi-quantitative ratio of Ni4+∶Ni3+=60∶40 which presented no significant change with increase of sintering time. After sintering for up to 11 h at 700°C, ordered Li0.61Ni0.96O2.0 ceramics were formed (R3m, a0=0.2837 nm, c0=1.417 nm). Distribution of the crystallite size was in the range of 80–200 nm. As sintering times were increased, the crystallite shapes exhibited a more distinct morphology, and the ordering degree of the cations was enhanced, while the conductivity was sharply enhanced up to 2.0×10−1 Ω−1 cm−1 at 30 °C. Compared to conventional ceramic and solution methods, the ordered nanophase Li0.61 Ni0.96O2.0 ceramics was obtained at 700 °C with shorter sintering times (≈ 11 h).