Preparation of Pb-Ca Master Alloy by Molten Salt Electrolysis

Abstract

Lead-acid batteries (LABs) are commonly utilized in various applications such as electric motorcycles, uninterruptible power systems, and stationary energy storage devices. Calcium (Ca) is an essential element being added to Pb grid alloys to increase their mechanical strength. In this paper, molten salt electrolysis is used to prepare Pb-Ca master alloy in molten CaCl2-NaCl at 700 °C. The Ca concentration reaches 2.51 wt%, and the current efficiency reaches 85.0% for the 1 A-scale electrolyzer and 75.8% for the 50 A-scale cell. Compared with the traditional physical mixing ways, Ca is selectively and gradually deposited in the liquid Pb cathode without worrying about the immense heat generated by mixing Ca and Pb. In addition, molten salt serves as a media to avoid the oxidation of Ca. Through thermodynamic calculations and electrochemical measurements, the Pb-Ca formation prefers to happen rather than Pb-Na alloy in molten CaCl2-NaCl because of the stronger interaction of Ca and Pb than Na and Pb. Overall, this paper provides a straightforward strategy to prepare Pb-Ca master alloys, which can be expanded to prepare various liquid semimetal alloys containing reactive metals.