Operating Performance of an Fe-Ti Stationary Redox Battery in the Presence of Lead

Several electrochemical energy storage batteries are under development for bulk energy storage (1, 2). One such battery that has undergone rapid develop-ment over the past several years i the redox battery (3, 4). Of the many possible redox systems, Fe-Cr /E ~---- 1.18V (5, 6) and Fe-T i /E ~---- 0.67V (4, 7, 8-10) have received the most attention. Recent analys.is of the Fe-Ti system indicates that the t i tanium half-cel l re-action dur ing discharge is the rate- l imit ing one (7-9). Improvement in the performance of this hal f-cel l is necessary for the Fe-T i system to become an attractive energy storage device. We suspected earl ier that the kinetic activation l imitations in the t i tanium half-cel l might be caused by part ia l blockage of active anodic surface area by TiO = passivation. The TiO2 precipitate is most l ikely the result of a reaction between the t i tanium (IV) oxide with water in the bulk electrolyte. Schemati-cally, this reaction sequence can be represented as Ti+3 + H~O--> TiO + ~ + 2H + + e-(anodic charge transfer eaction