An Electrochemical Approach to Prepare Liquid Sodium-Lead Alloy using a Molten NaCl–Na2CO3 Electrolyte

Alloying alkaline metals (AMs) and/or alkaline-earth metals (AEMs) with lead (Pb) is an effective way to increase the mechanical strength of Pb alloys that are commonly employed as grids of lead-acid batteries (LABs). However, current methods for making AM/AEM-Pb alloys by physically mixing pure AM/AEM and Pb face challenges such as instantaneous thermal runaway from exothermic alloy reactions and oxidation of AM/AEM. Herein, sodium-lead (Na–Pb) alloy is directly prepared by molten salt electrolysis without generating Cl 2 gas using a molten NaCl–Na 2 CO 3 electrolyte with a current efficiency of above 80 pct at 200 mA·cm -2 , because the discharge of CO 3 2− is significantly more favorable than that of Cl − at the graphite anode. Furthermore, the reduction of Na + on the liquid Pb electrode happens at a potential more positive than the reduction of pure Na. The diffusion coefficient of Na in liquid Pb is measured as 3.22 × 10 −4  cm 2  s −1 at 750 °C by the galvanostatic intermittent titration technique (GITT), and the simulated electrolysis current density is 200 mA cm −2 . Moreover, the prepared Pb–Ca–Na–Al using the electrolytic Na-Pb alloys achieves a significant mechanical strength improvement (27 pct increase of the hardness, 60 pct increase of the creep resistance). Overall, molten salt electrolysis offers a clean and efficient method for preparing various Pb alloys for next-generation LABs and other applications.