RESUMO
The lithiation/de-lithiation behavior of a ternary oxide (Li2MO3, where M = Mo or Ru) is examined. In the first lithiation, the metal oxide (MO2) component in Li2MO3 is lithiated by a conversion reaction to generate nano-sized metal (M) particles and two equivalents of Li2O. As a result, one idling Li2O equivalent is generated from Li2MO3. In the de-lithiation period, three equivalents of Li2O react with M to generate MO3. The first-cycle Coulombic efficiency is theoretically 150% since the initial Li2MO3 takes four Li(+) ions and four electrons per formula unit, whereas the M component is oxidized to MO3 by releasing six Li(+) ions and six electrons. In practice, the first-cycle Coulombic efficiency is less than 150% owing to an irreversible charge consumption for electrolyte decomposition. The as-generated MO3 is lithiated/de-lithiated from the second cycle with excellent cycle performance and rate capability.
RESUMO
We report on the synergetic effects of silicon (Si) and BaTiO3 (BTO) for applications as the anode of Li-ion batteries. The large expansion of Si during lithiation was exploited as an energy source via piezoelectric BTO nanoparticles. Si and BTO nanoparticles were dispersed in a matrix consisting of multiwalled carbon nanotubes (CNTs) using a high-energy ball-milling process. The mechanical stress resulting from the expansion of Si was transferred via the CNT matrix to the BTO, which can be poled, so that a piezoelectric potential is generated. We found that this local piezoelectric potential can improve the electrochemical performance of the Si/CNT/BTO nanocomposite anodes. Experimental measurements and simulation results support the increased mobility of Li-ions due to the local piezoelectric potential.