Electrochemical properties of Ca–Pb electrode for calcium-based liquid metal batteries

The Ca–Pb electrode couple is considered to be one of the least expensive (~36 /(kW·h)) among various optional materials for liquid–metal batteries (LMBs). The electrochemical properties of Ca–Pb alloy in a Ca|LiCl–NaCl–CaCl₂|Pb cell were investigated in this paper. The electrode potential maintained a linear relationship in the current density range of 50–200 mA·cm⁻², which indicates that the alloying and dealloying processes of Ca with Pb attained rapid charge transfer and mass transport in the interface between the liquid electrode and electrolyte. The Ca–Pb electrode exhibited remarkable properties with a high discharge voltage of 0.6 V, a small self-discharge current density (<2 mA·cm⁻² at 600°C), and a high coulombic efficiency (>98.84%). The postmortem analysis showed that intermetallics CaPb₃ and CaPb were uniformly distributed in the electrode with different molar fractions of Ca, which indicates that the nucleation of solid intermetallics did not hinder the diffusion of Ca in the electrode. This investigation on Ca–Pb electrode sheds light on the further research and the design of electrodes for Ca-based LMBs.