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 density—a measure of energy storage capacity—is 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— Ν

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