DISCUSSION SECTION 1271tion of the amount of stored electrostatic charges (E = q/C, for a linear capacitor).P. J. Nigrey, 23 D. MacInnes, Jr.,23 D. P Nairns, 23 A. G. MacDiarmid, 23 and A. J. Heeger:24 The suggestion by Dr. Schuldiner that partially oxidized polyacetylene, (CH)x, e.g., , when used as the cathode in a (rechargeable) battery is actually a positively charged electrolytic capacitor plate was based on the assumption that the potential (E) of the polyacetylene cathode would be a simple function of the amount of stored electrostatic charge (E : q/c for a linear capacitor, where q --the magnitude of the stored electrostatic charge and c --the capacitance of the polyacetylene electrode). This assumption is incorrect.We have found during work carried out subsequently to submission of our paner discussed above that when the open-circuit voltage, Voc, of a (CH)~/1M LiC104 in propylene carbonate/Li cell is plotted as a function of the charge stored in the polyacetylene, the potential shows only a relatively small dependence on the magnitude of the stored charge above a doping level of ca. 1%, the semiconductor-metal transition. 25 Voc values were recorded at intervals during charging together with the amount of charge stored in the polyacetylene. In order to allow for some equilibration of the (C104)-ions in the (CH)x fibrils, the Voc values were measured, in each case, 5 min after the d-c power supply was disconnected. Charging was then immediately restarted to obtain further data points. The potential of parent, nonoxidized (CH)~ vs. a standard lithium electrode in this electrolyte is ca. 2.5V. The potential of the polyacetylene cathode increases by ca. 1.0V (to ca. 3.5V) on oxidizing it to 1% and increases an additional 0.3V (to 3.8V) on oxidation from 1 to 6%. Contrary to a conventional electrode, the potential of the polyacetylene cathode is not expected to be independent of the total quantity of stored electroactive species, since unlike a conventional cathode, the chemical composition (oxidation state) of the polyacetylene is constantly changing during the charging process from (CH~ to (CH+a)z to (CH+a+b)x to

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The relationship of cell potential to degree of oxidation, coulombic and energy efficiencies, constant-current discharge characteristics, energy density and maximum power density of a partly oxidized polyacetylene, [CH(ClO,),] 0, < 0.07), cathode in a cell of the type [CH(ClO,),],ILiClO,ILi are discussed. Coulombic efficiencies ranging from 100 to 86 % and energy efficiencies ranging from 8 1 to 68 %during a chargedischarge cycle are found at oxidation levels ranging from 1.54 to 6.0%. Energy densities of ca. 255 W h kg-' (based on the weights of the electroactive materials involved in the discharge process) are obtained for 7.0% oxidized polyacetylene cathodes under constant-current discharge conditions. Maximum power densities of ca. 30 kW kg-' are observed.

Polyacetylene, false(CH)x can be controllably doped electrochemically through the semiconducting to the metallic regime using a solution of LiClCO4 in propylene carbonate and a lithium cathode. Flexible, golden, free‐standing films of false[CH+yfalse(ClO4)y−]x false(y=0 normalto 0.06false) having conductivities up to ∼103Ω−1 cm−1 are readily obtained. Electrochemical “undoping” of the false[CH+yfalse(ClO4)y−]x allows this doped film to be used as the cathode‐active material in lightweight rechargeable storage batteries. The overall complete discharge reaction isCH+0.06)(ClO40.06−x+0.06xnormalLi→CHx+0.06xLiClO4A 0.5 cm2 piece of the 6% doped film ( 1.0×0.5×0.01 normalcm ; ∼3 mg) exhibited an open‐circuit voltage of 3.7V and an initial short‐circuit current of 25 mA. No change in the open‐circuit voltage characteristics of a battery could be detected even after 326 successive constant current partial charge/discharge cycles. No degradation of the polyacetylene electrode was observed. Experimental energy densities of ∼176 W‐hr/Kg were obtained based on the weight of the false[CH+0.06false(ClO4−)0.06]x initially employed and the weight of Li consumed (exclusive of weights of electrolyte, solvent, and packaging material) during partial discharge when false[CH+0.06false(ClO4)0.06−]x was converted to false[CH+0.024false(ClO4)0.024−]x .

Application of dynamic signal analyzers to selected electroacoustical measurements.Electrochemical techniques are applied to a study of selected intrinsic physical properties (independent of dopant) of polyacetylene, (CH) x' Electrochemical voltage spectroscopy (EVS) is used to characterize the energies of charge injection and removal for both cis-(CH) x and trans-(CH) x' The difference in charge injection and ejection potentials is shown to give a direct measure of the approximate semiconductor band gap and the results are compared with similar data from optical measurements. Charge injection and ejection potentials are used to define the redox potentials of (CH)x and are used in conjunction with equilibrium potential measurements at varying oxidation or reduction levels of polyacetylene to present a unifying concept to the electrochemistry of (CH) x • Electrochemical voltage spectroscopy techniques described previously7 can be modified if one is interested only 5102