Reconstruction of Lead Acid Battery Negative Electrodes after Hard Sulfation Using Controlled Chelation Chemistry

Lead acid batteries (LABs) remain an inexpensive energy storage technology with a wide application base. However, their short cycle lifetimes necessitate improved recycling and maintenance technologies to combat their various failure modes. One major cause of failure is hard sulfation, where the formation of large PbSO4 crystals on the negative active material impedes electron transfer. Here, we introduce a protocol to remove hard sulfate deposits on the negative electrode while maintaining their electrochemical viability for subsequent electrodeposition into active Pb. Soaking the hard sulfate negative electrode in an alkaline EDTA solution reshaped the surface by solubilizing PbSO4 to Pb-EDTA while avoiding underlying Pb phases. Thereafter, we explored electrodeposition of the Pb-EDTA complex as fresh electrode material and found reduction of Pb-EDTA required lower deposition overpotentials with decreasing pH. We used electrodeposited films on gold to demonstrate cycling of the restored active Pb in H2SO4. The film's capacity gradually faded with cycling and PbSO4 formation, alike to commercial LABs. Lastly, we demonstrated the electrodeposition of Pb directly onto negative electrodes from a commercial LAB. Our unique approach seeds opportunity for recycling the electrode materials inside LABs without disassembly or extensive material processing.