BASF/Varta

Work with PPy and PAni has reached the industrial stage. Bridgestone-Seiko has been selling coin-shaped 3-V polyaniline-based batteries for 5 years (1987-1992), and polypyrrole-based batteries were developed by Varta/BASF in the same period. Such batteries have lower energy densities than those of conventional batteries, but they are superior in terms of selfdischarge. The main characteristics of a typical PAni battery are compared to those of lead and Cd-Ni batteries in Table 4. The values mentioned for energy density and electric capacity density refer to the active material alone. 

A polypyrrole battery has been developed and tested by BASF and VARTA Baterie AG. The positive electrode consisted of electrochemically synthesized polypyrrole doped with tetrafluoroborate. When PPy is used with a lithium counterelectrode at a cell voltage of 3.5 V, a thoretical energy density of 360 W h/kg is estimated for the PPy electrode, although in a practical cell the density is lower [428 30],... 

In Europe BASF, in cooperation with Varta Batteries AG, Kelkheim, has successfully produced commercial PPy, and the production of batteries with capacities of 90 A h kg is to be expected in the near future [89,94]. The prototype cells of the type PPy (positive electrode)/LiC104-PC/Li (negative electrode) exhibit excellent charge/discharge characteristics, having undergone some 500 cycles with minimal effect on performance. The construction of the battery is of cylindrical sandwich type. 

In a 1997 review, electrochemically active polymers - including also PT - for rechargeable batteries are given [71]. In this review the first two really produced batteries containing polymeric materials are described intensively with their special problems [72] (i) the German Li/polypyrrole battery (Varta-BASF battery) [73-75] and (ii) the Japanese Li/polyaniline battery [75]. 

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