ACS staff returns to renovated headquarters

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  • But the new measures could have further impact. Once Congress sets up a risk-based system for writing cost-effective rules, business leaders and state and local officials may seek to change existing laws. And the one law most vulnerable to tinkering is the Clean Air Act, which these critics see as dictating costly and proscriptive pollution controls.

    Ironically, Republicans may be reinventing the wheel with their risk bill. The Administration has already undertaken an internal effort to make rule making more efficient and cost effective. For the past six months, White House officials have been leading an interagency review of the role of risk assessments and cost-benefit analyses in regulatory decision making.

    Lois Ember

    Organic cathode spurs battery energy storage Scientists in Japan have used a composite organic cathode to increase the amount of energy that can be stored in a rechargeable lithium battery. The development "is likely to prove advantageous in applications where weight, rather than volume, is a critical factor/' the researchers say.

    The cathode, based on a mixture of a dimercaptan and polyaniline, can be repeatedly charged and discharged. Its gravimetric energy densitya measure of energy storage capacityis at least one and a half times higher than that of the lithium cobalt oxide (LiCo02) cathode, which is one of the highest energy density cathodes currently used in commercial lithium batteries.

    Oxides such as LiCo02 are used in the carbon-based lithium "rocking-

    chair" batteries that are beginning to replace conventional batteries in portable electronic equipment such as laptop computers and cellular phones. Also known as "lithium ion" batteries, these devices use carbon or insertion compounds such as graphite intercalated with lithium as anodes.

    The new composite electrode was developed by chemistry professor Noboru Oyama, research associate Te-tsu Tatsuma, and graduate student Toshitada Sato at Tokyo University of Agriculture & Technology, and Tadashi Sotomura, a researcher at Matsushita Electric Industrial Co., Osaka [Nature, 373, 598 (1995)].

    "We have employed the composite cathode to prepare thin, flexible, film-type batteries," Oyama says. The cathode is less expensive to prepare and less polluting than conventional heavy-metal-oxide cathodes, he says.

    The cell used by the group to test the cathode has a solid polymer electrolyte film sandwiched between a lithium foil anode and the cathode film. The electrolyte film is prepared from a solution of ethylene carbonate, propylene carbonate, and acrylonitrile methylmethacry-late copolymer. The solution is diluted with acetonitrile and dried.

    The Japanese researchers prepare the composite cathode material from an N-methyl-2-pyrrolidone solution of 2,5-dimercapto-l,3,4-thiadiazole (DMcT) and chemically polymerized polyaniline. The concentrated solution is dark and viscous like ink. It is spread on a carbon film and dried under vacuum.

    Preparation of the material in this way allows intimate molecular-level mixing between DMcT and polyaniline, both of which are electrochemical-ly active at the cathode. "Charge transfer between DMcT and polyaniline is fast even at room temperature, proba-

    ACS staff returns to renovated headquarters Renovation of the American Chemical Society headquarters at 1155 16th St. in Washington, D.C., has been completed two months ahead of schedule. The first group of ACS staff members will move back from temporary facilities at 1120 Vermont Ave. over the weekend of Feb. 24-26, and a second contingent will move on the weekend of March 3-5. Beginning Feb. 23, and until the move is completed, ACS members calling headquarters may experience difficulty reaching some staff members. Total revamping of the ACS building, constructed in 1960, began in May 1994 and was expected to take a year. The design for the $11.5 million renovation was developed by the architectural firm Hickok-Warner of Washington, D.C., under the direction of the society's Property Development Committee.

    bly because of the chemical interaction between DMcT and polyaniline," Oyama suggests.

    Dimercaptans have been investigated as possible cathode-active materials for several years. Oxidation polymerizes them and reduction depolymerizes them. But this redox reaction is too slow at room temperature for practical applications.

    Previous work by Oyama's group showed that polyaniline accelerates DMcT redox reactions. But those experiments used DMcT and polyaniline in powdered forms, limiting mixing of the two materials at the molecular level. The group says the new cathode's life, as measured by cyclic performance, is "much better than that of the mixed-powder cathode."

    Two redox reactions occur at battery cathode Glass plate

    Current collector " ^ ^ ^ > -l-P y

    Lithium anode

    Polymer electrolyte Composite cathode Current collector

    Glass plate

    Polyaniline

    N-N

    LiS SLi

    DMcT Test cell

    -to-K>4 - e > L i +

    +e ,+Li+

    FEBRUARY 20, 1995 C&EN 5

    ACS staff returns to renovated headquarters