A closed-loop acetic acid system for recovery of PbO@C composite derived from spent lead-acid battery

•A closed-loop acetic acid route to recover spent lead paste is first proposed.•Key parameter of nCit3-/nPb is optimized as 2/3 for lead citrate crystallization.•Up to 95% of acetic acid could be recycled in filtrate recirculation process.•The leaching ratio of Pb is kept as 95% in seven batches of filtrate recirculation.•Cell with PbO@C composite showed an 8% higher initial capacity than the control group.