A conversion reaction mechanism of Cu 3 B 2 O 6 during the electrochemical reduction in a Li-ion battery test cell was revealed. Different experimental techniques were used: X-ray diffraction (XRD), in situ synchrotron diffraction, quasi in situ X-ray photoelectron and Auger-electron spectroscopy (XPS and AES), and ex situ scanning electron microscopy (SEM). The reduction process changes the initial oxidation state of copper from Cu(II) to Cu(0). After the subsequent oxidation, only the Cu(I) state was recovered. However, a very high amount of carbon in the cathode mixture (65% w/w) enables the reversion of the Cu(II) state due to improved electronic conductivity. Synchrotron in situ diffraction did not indicate any significant change in the lattice parameters of Cu 3 B 2 O 6 during any stage of reduction, which excludes a Li-intercalation mechanism. The present rechargeable lithium-ion batteries operate based on intercalation processes. These processes require electrode materials with open crystallographic structures, into which lithium ions can be inserted without reconstructive phase transitions. The change of the metal oxidation state is therefore limited by the available vacant sites for Li-ions in the underlying crystal structures. Higher capacities can be achieved in a conversion reaction, which does not preserve the initial structure type.
The so-called Bayesian reasoning is applied whenever uncertainty has to be considered as serious factor in interpretation of results. The paper presents analysis of the impact of inaccurate data on the straight line and quadratic relation fittings. This type of analysis is particularly important when one tries to decide on the type of dependence. The paper also shows examples of the Maximum Entropy Methods applied to the reconstruction of the hyperfine parameters distribution from the measured Mössbauer spectra of GaFeO 3 and the electron-positron momentum distribution from the positron annihilation data of Gd.
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