Polythiophene lithium battery electrodes

The electrosynthesis of polythiophene (PT) from thiophene must be performed under extremely anhydrous conditions, quite in contrast to polypyrrole [334]. Polymerization of 3-methylthiophene and bithiophene is much less sensitive to water. The advantage of PT is a higher theoretical capacity and a very positive potential (cf. Table 7). It is for these reasons that its application as a positive electrode in rechargeable lithium batteries [335-338] and in a metal-free PPy/PT cell [339] has been considered. Derivatives such as dithienothiophene [340] or rra/is-l,2-di(2-thienyl)ethylene [341] have also been polymerized, but the polymer materials suffer from low theoretical capacities [337]. 

Polythiophene (from bithiophene) was also proposed as the positive electrode in a rechargeable lithium battery [505, 506]. All solid-state batteries were assembled with PEO/LiC104. Poly(3-methylthiophene) was used in Li/S02 rechargeable cells [507]. 

A major goal of the research on conducting polymers has been the development of a rechargeable plastic battery. Cells based on polypyrrole and lithium electrodes have been developed in which the energy per unit mass and discharge characteristics are comparable to nickel-cadmium cells. Current interest appears to center around stable, processable polymers, such as polythiophene and its derivatives, and polyaniline. 

The maximum energy and power densities of n- and p-dopable polythiophene derivatives have specific capacities (10-15 Ah/kg) that are 5-6 times higher than those of high surface area carbonaceous electrodes [150]. However, compared with cathode materials of lithium secondary batteries, such as LiCo02 or LiNi02 (around 100 Ah/kg), the specific capacities of current polythiophene derivatives are approximately an order of magnitude lower. 

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