Effect of the lead deposition on the performance of the negative electrode in an aqueous lead–carbon hybrid capacitor

Lead-carbon hybrid capacitors are the electrochemical devices between supercapacitors and lead-acid batteries, with low prices, stability in high and low temperature, good security and broad application prospects. This paper introduces an electrodeposition behavior of Pb2+ on the negative electrode, which can improve the cycle life of the lead–carbon hybrid capacitor. During the charging process, lead ions in the electrolyte can diffuse from the positive electrode of the lead–carbon hybrid capacitor into the negative electrode. When charging at a low current density, the lead ions around the negative electrode can be reduced to lead, and it is then quickly converted to lead sulfate crystals. With the increase of the number of cycles, the final result is sulfation. Sulfation can reduce the specific surface area of the electric double layer, thereby reducing the capacitance performance of the carbon material. As a result, it reduces the charge–discharge efficiency of the lead–carbon hybrid capacitor. The service life of lead–carbon hybrid capacitor is significantly improved by the inhibition of lead deposition by anion exchange membrane. The capacity retention rate at 5 A/g is improved from 84% after 1000 cycles to 95% after 10,000 cycles. The discovery of lead deposition in the negative electrode is conducive to improving the performance of long-life lead–carbon hybrid capacitors.