Inducing and real-time monitoring of lead (de)sulfation processes using scanning electrochemical microscopy for applications in the refurbishment of lead-acid batteries

Lead acid batteries (LABs) remain as a mature, cost-effective energy storage technology for a wide variety of applications. Hard sulfation is one of the primary reasons for the short lifetime of LABs. This phenomenon is primarily characterized by the formation of large, non-redox active crystals of PbSO₄ which reduce the negative active material utilization by slowing down the electron transfer (ET) kinetics on the surface. Here, we report a microelectrochemical technique based on the surface interrogation mode of scanning electrochemical microscopy (SI-SECM) to locally probe the phenomenon of sulfation and the loss of ET therein. Thereafter, we validate our technique through an existing in-situ refurbishing strategy for sulfated anodes using EDTA-based chelation treatment and the recovery of ET. Energy dispersive X-ray spectroscopy (EDX) was used to verify the formation of PbSO₄ and its subsequent removal post treatment. We propose that our reported microelectrochemical technique promises to be useful in evaluating possible chelator candidates for the refurbishment of sulfated LABs. Finally, we also introduce ammonium acetate as a promising chelator candidate for the removal of PbSO₄ and use our proposed technique to evaluate the superior recovery of ET during ammonium acetate refurbishment. We hope this technique will be useful in evaluating the surface treatment of LABs and other energy storage electrodes which undergo redox-induced passivation processes.