Mechanistic Interfacial Electrochemical Characteristics of Graphene Enhanced Optimized Lead Acid Battery Cathode

Abstract

Graphene additives have been rightly used in enhancing the capacity and cyclic performance of lead acid battery. However, the fundamental mechanisms of the enhancements in terms of electrochemical characteristics is still unclear. This study focuses on the mechanistic understanding of graphene enhancements within the interphase of the lead acid battery positive electrode in terms of charge transfer resistance and double layer capacitance on adding three graphene additives of pristine graphene, reduced graphene and graphene oxide. Reaction kinetics is greatly enhanced by reduced charge transfer resistance and high electroactive surface area (Rct) which ensures fast desorption of ions at the agglomerate interphase. Significant reduction in Rct of reduced graphene optimized samples was resulted from its larger size due to agglomeration. Electrochemical double layer capacitance or surface charge capabilities enhances discharge performance. Optimized samples had lower charge transfer resistances and were marked by increased peak current values indicating increased faradaic and non-faradaic pseudo-capacitive processes. GO, CCG and GX within the electrode interphase has the capability to store charges in the presence of H+/OH- ions. The double layer capacitances of the graphene electrodes were higher at maximum charge partly due to agglomeration in the CCG, and similarly with GX which has a higher conductivity.

Keywords: capacitance; graphene; interphase; charge transfer; lead battery