Hiromori Tsutsumi

Layered-Structure BC[sub 2]N as a Negative Electrode Matrix for Rechargeable Lithium Batteries

This paper reports on a new compound with graphite-like structure, BC[sub 2]N which has been synthesized by a vapor-phase reaction of acetomtrale (CH[sub 3]CN) and borontrichloride (BCl[sub 3]). The electrochemical behavior of BC[sub 2]N was investigated in propylene carbonate (PC)-based solutions containing lithium (Li) salts. Cyclic voltammetric curves of the BC[sub 2]N electrode showed current increases during the cathodic potential scans and corresponding peaks at ca. 1.5 V in the anodic scans. The cathodic currents were accompanied by electrochemical intercalation of Li from the electrolyte, and the anodic peaks resulted from the deintercalation of Li from the BC[sub 2]N electrode. The polarization behavior of Li with the BC[sub 2]N matrix depended on the solvent as well as the salt of the electrolytic solution. The coulombic efficiency for charge/discharge cycling under a constant current was 90% or higher in LiClO+PC. The results indicate that BC[sub 2]N is usable as a negative electrode matrix for rechargeable Li batteries.

Polarization Behavior of Lithium Electrode in Solid Electrolytes Consisting of a Poly(Ethylene Oxide)‐Grafted Polymer

A complex of poly(ethylene oxide)-grafted poly(methyl)-methacrylate (PEO-PMMA) with a lithium salt has been examined as a solid electrolyte of an ambient-temperature rechargeable lithium battery. The coulombic efficiency of lithium during the charge-discharge cycle depended on the cycling current density. The average efficiency reached 88% at 50 μA cm −2 cycling when an Al plate was used as a substrate

Polyaniline‐poly[p‐styrenesulfonic acid‐co‐methoxyoligo(ethylene glycol)acrylate] Composite Electrode for All‐Solid‐State Rechargeable Lithium Battery

Polyaniline-poly[p-styrenesulfonic acid-co-methoxy-oligo(ethylene glycol)acrylate] composite (PANI-PSSA-co-MOEGA) electrode was prepared for an all-solid-state rechargeable lithium battery and a Li/PANI-PSSA-co-MOEGA model cell was fabricated by combining a cross-linked poly(ethylene oxide)-grafted poly(methylmethacrylate)/LiClO 4 polymer electrolyte. PSSA-co-MOEGA dopant has anchored anion sites (benzenesulfonic acid site) for doping polyaniline and oligo-ethylene oxide side chains for improving the adhesion between the electrode and the polymer electrolyte. Li/PANI-PSSA-co-MOEGA cell exhibited good cyclability and high capacity over 40 cycles. A model cell was also assembled by using a polyaniline electrode doped with perchlorate anion, PANI-CIO 4 , and the capacity of Li/PANI-ClO 4 cell decreases over 10 cycles. The differences are caused by two factors. First, the PANI-PSSA-co-MOEGA composite film became a partially cation-doped type polymer (by doping polymer anion). Second, the interface between the PANI-PSSA-co-MOEGA electrode and the polymer electrolyte is improved by incorporating the oligo-ethylene oxide side chains in both materials. The diffusion rate of the dopant ions in PANI-PSSA-co-MOEGA was faster than in the PANI-ClO 4 film.

Asymmetric anionic polymerization of maleimides bearing bulky substituents

Asymmetric anionic homopolymerizations of N-substituted maleimide (RMI) bearing bulky substituents [R = benzyl, diphenylmethyl (DPhMI), 9-fluorenyl (9-FlMI), triphenylmethyl, (diphenylmethyloxycarbonyl)methyl, (9-fluorenyloxycarbonyl)methyl] were carried out with complexes of organometal compounds (alkyllithium, diethylzinc) with six chiral ligands to obtain optically active polymers. The chiroptical properties of the polymers were affected strongly by the substituents on nitrogen in the maleimide ring, the organometal and chiral ligands. Poly(DPhMI) initiated by an n-butyllithium/(−)-sparteine (Sp) complex showed a positive specific rotation ([α] +60.3°). Poly(9-FlMI) prepared with a florenyllithium/Sp complex exhibited the highest specific rotation (+65.7°). The specific rotations of the poly(RMI) obtained were attributed to different contents between the stereogenic centers (S,S) and (R,R) based on threo-diisotactic structures of the main chain.

Asymmetric polymerization of N-substituted maleimides with chiral oxazolidine-organolithium

Asymmetric anionic homopolymerizations of achiral N-substituted maleimides (RMI) were performed with lithium 4-alkyl-2,2-dialkyloxazolidinylamide. All obtained polymers were optically active, exhibiting opposite optical rotation to that of a corresponding oxazolidinyl group at the terminal of the main chain. This suggests that opposite optical rotation to the corresponding chiral oxazolidine was induced to the polymer main chain. In the polymerization using a fluorenyllithium (FlLi)–oxazolidine complex, the obtained polymer with a fluorenyl group at the polymer end showed a negative specific rotation. This also suggests that asymmetric induction took place in the polymer main chain. The asymmetric induction was supported by the circular dichroism (CD) and GPC analysis with polarimetric detector. Optical activity of the polymer was attributed to different contents of (S,S) and (R,R) structures formed from threo-diisotactic additions, as supported by the 13C-NMR spectra of the polymers and the model compounds.

Synthesis and polymerization of Chiral methacrylates bearing a cholesteryl or menthyl group

Chiral methacrylates, that is, cholesteryl (ChMOC) and l-menthyl (MnMOC) N-(2-methacryloyloxyethyl)carbamates, were synthesized from 2-methacryloyloxyethyl isocyanate and cholesterol and l-menthol, respectively. Radical polymerizations of ChMOC and MnMOC gave number-average molecular weights for poly(ChMOC) and poly(MnMOC) of up to 3.74 × 104 and 9.39 × 104, respectively, and the specific rotations ([α]) were −43.1° to −47.7° and −87.6° to −89.0°, respectively. Temperature dependence of the specific optical rotation was observed for poly(ChMOC) but not for poly(MnMOC). The hydrogen bonds based on urethane segments for poly(ChMOC) were stronger than those for poly(MnMOC) according to IR spectra. In addition, the chiroptical properties of poly(ChMOC) were slightly affected by temperature in the presence of trifluoroacetic acid acting as an inhibitor for the formation of hydrogen bonds. Therefore, poly(ChMOC) may have a regular conformation due to hydrogen bonds and interaction between cholesteryl groups. Radical copolymerizations of ChMOC with styrene, methyl methacrylate, N-cyclohexylmaleimide, and N-phenylmaleimide were performed with 2,2′-azobisisobutyronitrile in tetrahydrofuran at 60 °C. Monomer reactivity ratios and Alfrey–Price Q–e were determined. Chiroptical properties of the copolymers were influenced by co-units. Thermal and X-ray diffraction analyses were performed for the homopolymers and copolymers.

Conductivity enhancement of polyacrylonitrile-based electrolytes by addition of cascade nitrile compounds

Abstract A cascade nitrile compound ([CH2N(CH2CH2CN)2]2, ED4CN) made by addition of acrylonitrile to alkyldiamine (1,2-diaminoethane), has been used as a plasticizer for solid polymer electrolytes. The ionic conductivity of a polymer electrolyte using this type of plasticizer in polyethylene oxide (PEO)– and polyacrylonitrile (PAN)–LiClO4 complex was measured. Addition of ED4CN to PEO-based electrolytes did not enhance the conductivity of them. However, interaction between ED4CN and lithium ions in the complex was confirmed by infrared spectroscopy. The peak assigned to the stretching vibration of nitrile group in ED4CN shifted to high-energy side. The shift indicated that the nitrile groups interacted with the lithium ions in the PEO-based electrolytes. Conductivity enhancement was observed in the PAN-based electrolytes containing ED4CN. Conductivity of the electrolyte containing ED4CN was about 10 or 23 times larger than that of the electrolyte without ED4CN. Addition of ED4CN to a PAN–LiClO4 electrolyte decreases the glass transition temperature of the complexes. Conductivity enhancement of the PAN-based electrolyte with ED4CN containing lithium salt in high concentration was also confirmed. Other low molecular weight additives, tetraethylsulfamide (TESA) and a cascade nitrile compound, ([CH2CH2N(CH2CH2CN)2]2, TE4CN) were also used and their possibility for a conducting enhancer of PAN-based electrolytes was tested. TESA was effective; however, TE4CN was inactive for a conductance enhancer of the PAN-based electrolytes.

Electrochemical behavior of new polyamides containing disulfide bonds and pyridine rings in organic electrolyte solution

Abstract Aromatic polyamides ( N - a , a = I – III ) containing disulfide bonds and pyridine rings in the polymer backbone are prepared by condensation of diacid, 6,6′-dithiodinicotinic acid (N) and the corresponding alkyl diamine ( a = I – III : NH 2 -( CH 2 ) n - NH 2 , n = 4, 6, 12) with interfacial polymerization technique. Electrochemical behavior of the polyamides is investigated by using polyamide carbon paste electrodes. All polyamides show the redox response due to cycling between disulfide and thiol (thiolate) in acetonitrile solution containing 0.1 mol dm −3 LiClO 4 . The redox response is remarkable and the capacity is high in acetonitrile electrolyte solution. Polyamides N-I, N-II and N-III, shows good cycleability and high utilization to their theoretical values. The N atom in the pyridine ring is effective for redox reaction of the disulfide bond in the polymer. The capacity of the N-II/graphite electrode at first cycle is 93 Ah kg −1 and utilization of the polymer is 67% of the theoretical value.

Electrosynthesis of poly(p-phenylene) films and their application to the electrodes of rechargeable batteries

Abstract Thick and homogeneous poly ( p -phenylene) (PPP) films have been synthesized by electropolymerization of benzene from a nitrobenzene solution containing LiAsF 6 and CuCl 2 under vigorous stirring. The morphology of the polymer film depended on the conditions of the electrolysis. The electrochemical properties of the films were investigated in propylene carbonate solutions dissolving different lithium salts. The redox reaction, accompanied with electrochemical doping/undoping of the anion from/to the electrolyte, was usable for the electrodes of rechargeable batteries with high energy density.

Ionic conductance of polymeric electrolytes containing lithium salts mixed with rare earth salts

Abstract Polymeric ion conductors consisting of poly(ethylene oxide)-grafted poly(methylmethacrylate) (PEO–PMMA) matrices that dissolve lithium salts and rare earth salts have been prepared by photo-induced radical polymerization of methacrylate monomers with a linear polyether (PEGDE). The ionic structure and conductance behaviour of the resulting electrolyte systems were investigated as a function of the electrolyte composition. Polymeric electrolytes containing lithium salts with rare earth cations showed higher ionic conductivity than that containing lithium salts only. The conductance behaviour of the mixed salt system is discussed from the experimental results of thermal analysis, Raman spectroscopy, transport number measurements and 7Li NMR.