A study on open circuit voltage reduction as a main drawback of Zn–polyaniline rechargeable batteries

The factors influencing the reduced open circuit voltage (OCV) of a Zn–polyaniline (PANI) rechargeable battery were investigated. The reduced OCV of battery at various number of charge/discharge cycles was measured and its relevance to the zinc anode and polymeric cathode was investigated. The results revealed that the battery OCV is reduced with the number of charge/discharge cycles. The composition of cathode surface and nature of electrolyte solution were evaluated by using scanning electron microscope (SEM) and spectrofluorimetric measurements, respectively. The decreased OCV was found cause by the cathode electrode. Although the SEM analysis showed that some zinc particles are adsorbed on the polymeric cathode electrode, this factor was not a major factor contribution to the OCV reduction. The spectrofluorimetric analysis of electrolyte solution revealed its increased hydroquinone (HQ) content with increasing charge/discharge cycles, as a result of the electrochemical degradation of the charged polyaniline. Consequently, the OCV of Zn–PANI rechargeable battery is reduced by chemical redox reaction of charged PANI with HQ.