Effect of Carbon Additives to the Negative Electrode of Sealed Lead Acid Batteries

The addition of high surface area carbon allotropes during manufacturing to the negative electrode of lead acid batteries is expected to be beneficial to the performance of the battery under certain conditions. The purpose of this study was to build fully functional test batteries using experimental formulations of activated carbon to evaluate their use in manufacturing. In theory, the addition of carbon improves the porosity, surface area, and conductivity of the negative active material (NAM). These improvements result in a lower internal resistance by enhancing ionic adsorption of electro active species on the electrode surface, mass transport by convection, migration in an electric potential gradient, and diffusion in a concentration gradient. Gains were observed in both charge acceptance, and number of cycles in a partially discharged state, also known as Partial State of Charge (PSOC) cycling. Four different formulations of NAM were used to manufacture 2 Volt (V) test cells. The cells were cycled to failure on a programmable power supply using a standardized PSOC cycling regime. The structure and composition of the experimental carbons and the NAM, both virgin and at failure, was analyzed using X-Ray Diffraction (XRD), Raman Spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurements, Energy Dispersion X-Ray (EDX), and Scanning Electron Microscope (SEM) techniques. The Sigma Aldrich carbon performed better than control in terms of 10 hour capacity, charge acceptance, and cycle life. Further study is advised to confirm reproducibility of results