Yoshio Nishi

Lithium ion secondary batteries; past 10 years and the future

Abstract Technologies of lithium ion secondary batteries (LIB) were pioneered by Sony. Since the introduction of LIB on the market first in the world in 1991, the LIB has been applied to consumer products as diverse as cellular phones, video cameras, notebook computers, portable minidisk players and others. Years of assiduous efforts and researches to improve LIB performances enabled LIB to play a leading role in the portable secondary battery market. In this article, the past 10 years’ technological achievement is traced and future possibilities are discussed.

The structure and mechanical properties of sheets prepared from bacterial cellulose Part 2 Improvement of the mechanical properties of sheets and their applicability to diaphragms of electroacoustic transducers

A sheet obtained from bacterial cellulose had a remarkably high modulus of elasticity as reported in Part 1 of this series. The Youngs modulus of a sheet prepared by squeezing and drying a gel-like pellicle of bacterial cellulose was found to be > 15 G Pa. In addition, it has been found that treatment of the gel-like pellicles or dried sheets of bacterial cellulose with alkaline and/or oxidative solutions improves the mechanical properties significantly, and the Youngs modulus of the resulting sheets approaches 30 G Pa. In this paper, improvement of the mechanical properties of bacterial cellulose sheets by the removal of impurities is investigated and the applicability of bacterial cellulose to diaphragms of electroacoustic transducers is discussed.

Phase segregation of LixMn2O4 (0.6<x<1) in non-equilibrium reduction processes

Abstract Chemical synthesis routes to Li x Mn 2 O 4 (0.15≤ x ≤1) in non-equilibrium reduction processes were developed to carry out detailed structural analysis. Non-equilibrium Li x Mn 2 O 4 (0.15≤ x ≤1) samples were prepared by chemical lithiation of λ-MnO 2 with LiI for 24 h; longer than 1 week was needed to reach true equilibrium at room temperature. The samples were characterized by X-ray diffraction analysis. The phase diagram was different from that in the equilibrium state; three cubic phases (phases A, B and C) were observed for Li x Mn 2 O 4 (0.15≤ x ≤1). There were two regions of two-phase coexistence: the region of 0.25 x x x

Composite materials reinforced with polyoxymethylene whiskers

Various composite samples reinforced with polyoxymethylene (POM) whisker crystals were prepared and their Youngs moduli were measured and analysed, on a theoretical equation, to estimate the modulus of the filler itself. Good reinforcement was obtained with matrix resins such as an epoxide and an unsaturated polyester, the results giving the modulus of the whisker to be approximately 1×1011 N m−2, i.e., almost equivalent to the ideal crystal modulus of POM. Some acoustic properties were investigated for sheet composite materials prepared with a polyolefin polymer for matrix. The sonic velocity attained was more than twice that of the matrix polymer, at larger filler contents, while the internal dynamic loss was maintained at a reasonably high level. Loudspeakers carrying diaphragms of the composite sheets showed improved frequency characteristics in the high-frequency region. Some morphological observations were made for the crystals embedded in resins.

Carbonaceous Materials for Lithium Ion Secondary Battery Anodes

Abstract Graphite, graphitizable carbon (soft carbon) and non-graphitizable carbon (hard carbon) have been investigated as anode materials for lithium ion secondary batteries. Graphite and hard carbon are now mainly put to practical use and both have their merits and demerits. In this article, characteristics and properties of graphite and hard carbon as lithium intercalation hosts are described and the possibility is discussed of novel hard carbon anode materials prepared from agricultural wastes such as bamboo saw dusts or coffee grounds.

Lithium-Ion Secondary Batteries with Gelled Polymer Electrolytes

GPBs with the comparable properties to conventional LIBs were developed in which block copolymer between VDF and HFP was used. The ratio of PHFP to PVDF in the copolymer was 3c7.5%and Mw is greater than 550,000.

Lithium ion secondary battery technologies, present and future

Since the introduction of lithium ion secondary batteries (LIB) in 1991,the ceaseless and remarkable improvement has been done and the energy density has been doubled. New classes of anode and cathode active materials with possibly large charge and discharge capacity are in the course of development and further improvement in LIB performances can be expected by their adoption. The present status and future trends of LIB are discussed here including new types of LIB with polymer gel electrolytes.

Preparation of High-Strength Materials from Bacterial Cellulose

A pellicle of bacterial cellulose has been found to give a strong sheet, the Young’s modulus being as high as 30GPa across the plane. Such a good mechanical properties is considered to originate in the unique fibrillar morphology in which micro-fibrils are tightly bound by inter-fibrillar hydrogen-bonds. The sheets had a good acoustic characteristics applied to manufacturing diaphragms of practical models. The raw material was also processed into a pulp which was useful for making strong papers and reinforcing ordinary pulp papers and mats of other fibrous materials.