Improving the Cycle-life of Naphthoquinone-based Active Materials by Their Polymerization for Rechargeable Organic Batteries

AbstractTo increase the cycle-stability of rechargeable batteries using an organic positive-electrode material, we synthesized a polymer from a 5,8-dihydroxy-1,4-naphthoquinone (DHNQ) skeleton, which potentially undergoes a four-electron transfer redox reaction. The polymeric material (PDHNQ) was synthesized by the condensation reaction between DHNQ and formaldehyde under acidic media conditions. The initial capacity of the electrode using the monomer (DHNQ), 193 mAh/g, quickly decayed to 56 mAh/g after 100 cycles. On the other hand, the electrode incorporating the prepared PDHNQ showed the higher initial discharge capacity of 256 mAh/g and a longer cycle-life, retaining about 133 mAh/g after 100 cycles

Dialkoxybenzoquinone-type Active Materials for Rechargeable Lithium Batteries: The Effect of the Alkoxy Group Length on the Cycle-stability

AbstractThe performance of 2,5-di-n-decyloxy-1,4-benzoquinone (DDBQ) as an active material for rechargeable lithium batteries was investigated. The prepared electrode in which DDBQ was incorporated showed an initial discharge capacity of 125 mAh/g(DDBQ) with an average voltage of 2.5V vs. Li+/Li. The obtained discharge capacity corresponds to a benzoquinone-based two-electron redox behavior. In the cycle-life test, the prepared DDBQ- electrode showed a relatively good performance; it maintained about 60% of the initial capacity after 20 cycles. The observed cycle-stability was compared to those of the other dialkoxybenzoquinones bearing shorter alkoxy chains, such as the methoxy, ethoxy, and propoxy groups. The correlation between the cycle-stability and the solubility in the electrolyte solvent was discussed

Atomistic Phase Transition Mechanism of Zero-Strain Electrode Material: Transmission Electron Microscopy Investigation of Li4Ti5O12 Spinel Lattice Upon Lithiation

The lithiation mechanism of electrode materials is important for understanding the basic reactions in Li-ion batteries. In particular, zero-strain materials have garnered interest owing to their stable charge–discharge performances. In this study, we investigated the atomistic phase transition mechanism of spinel Li4Ti5O12, a well-known zero-strain material, using high-resolution transmission electron microscopy. A single-crystalline Li4Ti5O12 (100) specimen was prepared and observed in situ at a lattice resolution under electron beam-assisted lithiation. The lattice fringes originating from the Li plane of the spinel crystal were anisotropically altered during phase transition, suggesting the asymmetrical site shifting of Li atoms during lithiation. This spontaneous symmetry-breaking mechanism for the phase transition is considered essential for the lithiation of the spinel lattice

Hydrogen trapping state associated with the low temperature thermal desorption spectroscopy peak in hydrogenated nanostructured graphite

Hydrogenated nanostructured graphite has been reported to exhibit a characteristic peak at around 600–800 K in thermal desorption spectroscopy (TDS). The origin of this peak is still controversial. We have reexamined it based on a combination Fourier transform infrared (FT-IR), electron diffraction, and electron energy-loss spectroscopy (EELS) study. The FT-IR spectrum of HNG exhibited an unknown broad absorption band at very low frequencies around 660 cm^{−1}, which almost disappeared by annealing up to 800 K. Electron diffraction as well as plasmon peaks in EELS detected unusual shrinkage and subsequent expansion of the graphene interlayer distance by hydrogen incorporation and desorption with annealing, which were well correlated with the change in intensity of the 660 cm^{−1} IR band. An energetically stable configuration was found by theoretical model calculations based on GAUSSIAN03. All the present results are consistent with our previous studies, which suggested that hydrogen is loosely trapped between graphene layers