Aqueous metal salt solutions were used as models to probe the origin of the species observed in the electrospray mass spectrum. A qualitative or semiquantitative correlation among different species was observed between electrospray responses and calculated equilibrium aqueous solution concentrations. Quantitative correlations were obtained, however, when ions that were identical in charge and similar in type were selected for comparison. In these experiments the ions experienced very similar electrospray-related processes and their effects on the responses were canceled in a comparison of these ions. Consequently, the relative abundances of these ions in the electrospray mass spectrum closely matched the calculated relative abundances in aqueous solution. Our results suggest that the basic principle that determines ionic distribution in the electro spray mass spectrum in aqueous solution chemistry.
The electrospray mass spectra of MX, and MX, salts (where X is typically halide or nitrate) in protic and aprotic solvents, and solvent mixtures were examined. Comparisons of species responses with equilibrium aqueous solution concentrations were made. For MX, salts, a good correlation between MOH' response and MOH' solution concentration was observed under conditions where the collision energy was nominally zero. Cu(I1) is easily reduced in acetonitrile to Cu(1); Cu(1) was the principal species observed in the electrospray mass spectrum of Cu(I1) in acetonitrile whereas Cu(I1) was the principal species observed in that of Cu(I1) in dimethyl sulphoxide. Gas-phase reactions between solvated clusters produced by electrospray and a second solvent vapour were examined. M3 + clusters were the principal ions observed when an aqueous solution of MX, was sprayed in the presence of aprotic solvent vapours.
EXPERIMENTAL
InstrumentationExperiments were performed on a SCIEX TAGA Model 6000E triple quadrupole mass spectrometer with an upper mass limit of -1400 m/z. The electrospray Crown copyright (Canada)
A stable
shell–core architecture Li2TiO3@Li1.17Mn0.50Ni0.16Co0.17O2 (LTO@LNCM) was successfully synthesized via in-site
synchronous lithiation. This architecture is designed based on the
fact that Li1.17Mn0.50Ni0.16Co0.17O2 will experience oxygen release and side reactions
when interacted with the electrolyte and is strengthened by means
of the diffusion interphase of Li2Ni
x
Co
y
Ti1–x–y
O3 between Li1.17Mn0.50Ni0.16Co0.17O2 and
Li2TiO3. Hence, the architecture functions as
follows: (1) the Li2TiO3 shell, which is chemically
stable, acts as a protective shell and (2) the Li2Ni
x
Co
y
Ti1–x–y
O3 transition
phase zone not only enhances the close adhesion of the core to the
Li2TiO3 outer shell but also has higher Li+ ionic conductivity due to doping. LTO@LNCM showed a much
higher rate capability and improved cycle performance, besides a higher
initial Coulombic efficiency. In particular, LNCM with 3 mol % Li2TiO3 delivered an initial discharge capacity of
306.1 mAh·g–1 at 0.1C (Coulombic efficiency
of 89.9%) and a rate capacity of 155.5 mAh·g–1 at 10C. At the same time, a reversible capacity of more than 149
mAh·g–1 after 240 cycles was achieved with
only 0.11% decay per cycle at 1C rate (2.0–4.8 V). Thus, based
on the collective results, we expect our LTO@LNCM with a motivating
Li2Ni
x
Co
y
Ti1–x–y
O3 transition phase zone to be a promising cathode
material for advanced lithium-ion batteries.
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