Electrochemical devices incorporating high-conductivity conjugated polymers

Abstract

The present invention includes the preparation of highly conducting conjugated polymers and their use as electrochemical actuators. A typical electrochemical actuator comprises a highly conducting, conjugated polymer for the anode or the cathode, or for both the anode and the cathode; suitable conjugate polymers have a conductivity ≧100 S / cm. The material may have any form, including films and fibers. A preferred shape is a strip or a fiber, where the fiber can be solid or hollow, although any shape may be used. Before use, the material may be treated, for example, by immersion in an acid, in order to dope / protonate the material or to introduce anions or to exchange the anion in the polymer for another anion. Other materials may be incorporated in the polyaniline to increase its conductivity or to provide other benefits, such as increased strength. Useful conducting polymers include monomers of anilines, pyrroles, thiophenes, phenylene vinylenes, and derivatives thereof.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application claims the benefit of Provisional Application Ser. No. 60 / 206,511 which was filed on May 22, 2000.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT [0002] This invention was made with government support under Contract No. MDA972-99-C-0004 awarded to Santa Fe Science & Technology, Inc. of Santa Fe, N. Mex. by DARPA. The government has certain rights in the invention.FIELD OF THE INVENTION [0003] The present invention relates generally to electrochemical devices, such as actuators, batteries, supercapacitors, sensors, light-emitting electrochemical cells, photoelectrochemical solar cells, and electrochromic cells and, more particularly, to electrochemical devices which include a high-conductivity conjugated polymer. BACKGROUND OF THE INVENTION [0004] Actuators are capable of changing form or shape in response to a stimulus or condition and, thereby, of affecting a transformation or action. Actuation ...

AI Technical Summary

Benefits of technology

[0026] Benefits and advantages of the invention include actuators that are light weight, quiet, soft, inexpensive, and require only low voltages for operation. Additionally, a more uniform potential can be applied to the entire conjugated polymer component and, therefore, the response of the actuator can be shortened, the efficiency increased, and the extent of volume change can be increased. Moreover, the polymeric materials do not require a metal layer along their length for use in other electrochemical devices. Aqueous electrolytes are no longer required for operation; in particular, actuators and other electrochemical devices that utilize organic solvent electrolytes, solid polymer electrolytes, or gel electrolytes can be produced. In the area of conjugated polymer actuators, the present invention permits operation of artificial muscle-like films or fibers tens or hundreds of centimeters in length, instead of the 3 cm length that have been previously reported.

Problems solved by technology

It is difficult to achieve high conductivity in conjugated polymers.

High conductivity has been reported for pure polyacetylene with aligned polymer chains; however, this material is unstable in an air atmosphere.

Such films are too resistive to undergo complete and timely oxidation / reduction without a conductive layer in contact with one film surface.

If the material is very resistive, then the material may not even be sufficiently electroactive to undergo oxidation / reduction reactions without a metal backing, film, or contact, along its length.

However, such metal layers are detrimental to the operation of the actuator because the metal (a) may corrode or react in the electrolyte; (b) may delaminate; and (c) may crack.

Furthermore, such metal layers add processing steps and expense to the production of actuators.

Metal layers are also incompatible with linear actuation; that is, expansion and contraction along the length of the actuator, because such layers induce bending (FIG. 3).

A bending actuator cannot generate as much force as a linear actuator because some of the energy is lost in the transformation from linear motion to angular motion and because of considerations of torque.

Large peak separation not only requires greater operating voltages, a disadvantage for actuator devices, but also results in a lower efficiency: the net amount of energy required to power the devices depends directly on peak separation.

No film conductivity was reported; however, the required slow cycling speed of 1 mV / sec is indicative of a low conductivity.

Takashima, 1997; in both references, films were cast in the EB form and subsequently doped which results in low conductivity.

Again, as in the case for actuators, if the conjugated polymer material is resistive, the material may not even be sufficiently electroactive to undergo electrochemical reactions without a metal backing, or contact, along its length, and electrochemical devices utilizing conjugated polymers generally incorporate a metal layer.

Such a metal layer may be detrimental to the operation of the device because the metal may corrode or react in the electrolyte.

In addition, a noble metal such as gold or platinum is usually necessary, and these are expensive.

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