The congruently melting composition of Lithium Niobate(LN) is 48.6mol% Li 2O,rather than stoichiometric 50mol%Li 2O.By means of conventional Czochralski(CZ) method,it is easy to grow the congruent LN crystal with high...The congruently melting composition of Lithium Niobate(LN) is 48.6mol% Li 2O,rather than stoichiometric 50mol%Li 2O.By means of conventional Czochralski(CZ) method,it is easy to grow the congruent LN crystal with high quality,but difficult to grow the stoichiometric LN crystal with homogeneous composition. In contrast to CZ method,Melting Zone(MZ) method makes use of the segregation of solute,and is likely to grow homogeneous crystal.By MZ method,we have grown near stoichiometric LN crystal (Li%mol=49.5%) from stoichiometric LN raw material. The difference between the raw material and the crystal is due to the volatilization loss of Lithium at the growing temperature.With 50.5mol%Li 2O LN raw material,stoichiometric LN crystal could be grown. Li rich LN solvent zone preplaced in the melting zone makes the crystal much more homogeneous than that without the solvent zone.The preplaced Li rich zone heightens the starting [Li] concentration of the liquid phase,so that the initial [Li] concentration of LN crystal is close to the stable value,and the process of stabilization is shortened.展开更多
Vanadium pentoxide xerogel films used for lithium rechargeable batteries were prepared from crystalline c-V2O5 by melt quenching method,then the electrochemical process of lithium intercalation into vanadium pentoxide...Vanadium pentoxide xerogel films used for lithium rechargeable batteries were prepared from crystalline c-V2O5 by melt quenching method,then the electrochemical process of lithium intercalation into vanadium pentoxide xerogel films was simulated with an equivalent circuit model, which was derived from the mechanism of electrode reactions. Measured electrochemical impedance spectra at various electrode potentials were analyzed by using the complex non-linear least-squares fitting method. The results show that impedance spectra consist of 2 high-to- medium frequency depressed arcs and a low frequency straight line. The high frequency arc is attributed to the absorption reaction of lithium ions into the oxide film, the medium frequency arc is attributed to the charge transfer reaction at the vanadium oxide/electrolyte interface and the low frequency is characterized by a straight line with a phase angle of 45° corresponding to the diffusion of lithium ion through vanadium oxide phase. The experimental and calculated results are compared and discussed focusing on the electrochemical performance and the state of charge of the electrode. Moreover, the high consistence of the fitted values of the model to the experimental data indicates that this mathematical model does give a satisfying description of the intercalation process of vanadium pentoxide xerogel films.展开更多
文摘The congruently melting composition of Lithium Niobate(LN) is 48.6mol% Li 2O,rather than stoichiometric 50mol%Li 2O.By means of conventional Czochralski(CZ) method,it is easy to grow the congruent LN crystal with high quality,but difficult to grow the stoichiometric LN crystal with homogeneous composition. In contrast to CZ method,Melting Zone(MZ) method makes use of the segregation of solute,and is likely to grow homogeneous crystal.By MZ method,we have grown near stoichiometric LN crystal (Li%mol=49.5%) from stoichiometric LN raw material. The difference between the raw material and the crystal is due to the volatilization loss of Lithium at the growing temperature.With 50.5mol%Li 2O LN raw material,stoichiometric LN crystal could be grown. Li rich LN solvent zone preplaced in the melting zone makes the crystal much more homogeneous than that without the solvent zone.The preplaced Li rich zone heightens the starting [Li] concentration of the liquid phase,so that the initial [Li] concentration of LN crystal is close to the stable value,and the process of stabilization is shortened.
文摘Vanadium pentoxide xerogel films used for lithium rechargeable batteries were prepared from crystalline c-V2O5 by melt quenching method,then the electrochemical process of lithium intercalation into vanadium pentoxide xerogel films was simulated with an equivalent circuit model, which was derived from the mechanism of electrode reactions. Measured electrochemical impedance spectra at various electrode potentials were analyzed by using the complex non-linear least-squares fitting method. The results show that impedance spectra consist of 2 high-to- medium frequency depressed arcs and a low frequency straight line. The high frequency arc is attributed to the absorption reaction of lithium ions into the oxide film, the medium frequency arc is attributed to the charge transfer reaction at the vanadium oxide/electrolyte interface and the low frequency is characterized by a straight line with a phase angle of 45° corresponding to the diffusion of lithium ion through vanadium oxide phase. The experimental and calculated results are compared and discussed focusing on the electrochemical performance and the state of charge of the electrode. Moreover, the high consistence of the fitted values of the model to the experimental data indicates that this mathematical model does give a satisfying description of the intercalation process of vanadium pentoxide xerogel films.
