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

Hydrogenation and Dehydrogenation Properties of R H Ni 5 (R H = Heavy Rare Earth) Binary Intermetallic Compounds * 1

We systematically investigated the hydrogenation and dehydrogenation properties for heavy rare earth-based binary R H Ni 5 (R H = Gd, Tb and Dy) intermetallic compounds and evaluated the correlations between crystallographic and thermodynamic properties. XRD analysis shows that all R H Ni 5 compounds crystallize in the hexagonal CaCu 5 -type crystal structure. In analogy to the light rare earth-based R L Ni 5 (R L = La, Pr, Nd and Sm) compounds both lattice constants of R H Ni 5 compounds decrease with increasing the atomic number of R H element due to the lanthanide contraction. On the pressure-composition (P-C) isotherms, GdNi 5 -H 2 system shows two well-separated pressure plateaux qualitatively similar to R L Ni 5 -H 2 systems. Looking over from Gd to Dy in the R H Ni 5 compounds, we find three specific dehydrogenation properties on the P-C isotherms: 1. The first plateau pressure (p P1 ) increases in this order (at around H/R H Ni 5 = 2.5) due to less stability of hydrogen in the unit cell by the lanthanide contraction. Linear correlations are also observed between log p P1 and the unit cell volume (V) which fall onto the same lines extrapolated from those observed in case of the R L Ni 5 compounds. 2. The second plateau (P2) tends to disappear because the P-C isotherm goes beyond the critical point of the phase transition. 3. Fairly flat first plateau separates into two parts in which a new plateau (PN) appears at low hydrogen content (H/R H N