Oxidation of Nickel in AlCl3-1-Butylpyridinium Chloride at Ambient Temperature

We have studied in detail the electrochemical reaction of nickel in several kinds of molar ratio-controlled molten salts consisting of AlCl(3) and 1-butylpyridinium chloride (BPC) at 40°C. We observed NiCl(2) as an oxidation product from nickel on the surface of the electrode in slightly acidic AlCl(3)/BPC salts with molar ratios of 1.05/1.0 and 1.1/1.0. However, in strongly acidic salt with the ratio of 1.5/1.0, NiCl(2) deposits on the electrode less than when in the above salts, and no NiCl(29) is observed in basic and neutral salts with the ratio of 1.0/1.0 or less AlCl(3) content. This suggests that [NiCl(4)](2−) ions form as the oxidation of nickel in such neutral and basic AlC(3)/BPC (salts)

Characterization of Bulk and Surface Chemical States on Electrochemically Cycled LiFePO4: A Solid State NMR Study

Bulk and surface chemical states were both investigated for electrochemically delithiated LixFePO4 using {7}Li and {31}P MAS NMR spectroscopy. The quantitative lithium extraction/insertion from LiFePO4 and the reversible two-phase reaction behavior between LiFePO4 and FePO4 were confirmed on electrochemical operation. The {7}Li and {31}P NMR spectra of the fully charged LixFePO4 evidenced a single Li-poor phase Li0.05FePO4 instead of a biphasic mixture of 0.05LiFePO4 and 0.95FePO4. Simultaneous growth of LixPOyFz was also shown as a surface film component on the charged electrodes, which dynamically increased and decreased in intensity during charging and discharging reactions, respectively. The electrode surface was further characterized with XPS to discuss the surface film formation during electrochemical cycles. Combined chemical state analyzes by NMR and XPS spectroscopies suggested that the degradation of LiPF6 salt occurred from the initial redox cycles, but that of solvent occurred after multiple cycling. The deposition of carbonaceous species would be related to a small capacity fading observed after the multiple charge-discharge cycles