A Long-Lasting Polyacetylene Battery with High Energy Density

Abstract

An n-(CH)/LiClO4/p-(CH) battery (1.0 M LiClO4 in propylene carbonate) prepared by passing 2.14 C (dopant concentration y=0.072) exhibited an open-circuit voltage of 3.5 V and an initial short-circuit current of 28 mA ((CH)x electrode; ∼4 mg). Experimental energy density of 424 W-hr/Kg (at a stored charge of 10.8 C (y=0.364), a liberated charge of 4.52 C and a mean voltage of 2.7 V) was obtained based on the weight of the (CH) x film (both electrodes; ∼8 mg). No degradation of the polyacetylene battery was observed even after 2000 successive charge/discharge cycles, each cycle consisting of a 10 min discharge at a constant resistance of 50 kΩ and a 10 min charge at 0.1 mA (a stored charge of 0.06 C (y=0.002)).

Electrochemically Active Polymers for Rechargeable Batteries

“…Acetylene gas at pressures ranging from a few Torr to one atmosphere and concentrated solutions of Ziegler-type catalysts such as Ti(OC 4 H 9 ) 4 −Al(C 2 H 5 ) 3 are needed for the polymerization reaction, in which a (CH) x film (or, at low catalyst concentrations, a (CH) x powder) is formed on surfaces wetted with the catalyst solution. Generally, cis -polyacetylene is formed when synthesized at low temperatures (≤−78 °C). , During heating or electrochemical cycling of the cis -(CH) x , the thermodynamically more stable trans -polyacetylene is formed. The polymer synthesized at −78 °C has a randomly oriented fibrillar structure with fibrils of 5 to 20 nm; the fibril diameter increases to 30 nm when synthesis occurs at +100 °C. , The specific surface area of polyacetylene films is typically about 40−60 m 2 g -1 .…”

“…The polymer synthesized at −78 °C has a randomly oriented fibrillar structure with fibrils of 5 to 20 nm; the fibril diameter increases to 30 nm when synthesis occurs at +100 °C. , The specific surface area of polyacetylene films is typically about 40−60 m 2 g -1 . Polyacetylene is oxygen sensitive and, therefore, contact with air should be avoided …”

“…Both positive and negative battery electrodes are typically constructed using as-synthesized (virgin, undoped) polyacetylene films. This material is insulating and has to be anion- or cation-doped by electrochemical or chemical oxidation or reduction to become electronically conducting before its utilization as a battery electrode. ,− ,,,− The doping is often performed electrochemically after the battery is assembled. However, especially for the negative electrodes, the use of electrochemically prereduced (precharged) polymer is convenient.…”

“…A wide variety of solvents and electrolytes has been used for the electrochemical anion doping; e.g. propylene carbonate (PC), CH 2 Cl 2 , and THF with LiClO 4 , ,− ,,,− ,− LiBF 4 , , (C 4 H 9 ) 4 NClO 4 , ,,, and LiAsF 6 . , The choice of the solvent seems to have insignificant influence on the anion doping level attained (Table .1).…”

“…The discovery that (CH) x can be reduced electrochemically to the n -doped state in the presence of alkali metal ions has resulted in a large number of publications on Li + doping. ,,,,,,, The doping levels and, thus, the specific charge that can be imparted to polyacetylene negative electrodes appear to be higher when THF, rather than PC, is used as the solvent (Table .1). Sodium ion-doped (CH) x battery electrodes have also been prepared …”