Performance and Corrosion Behavior of Na-based Liquid Metal Batteries under Different C-Rates

The increasing demand for grid-scale energy storage to stabilize energy supply has driven interest in liquid metal batteries, which offer simple design and ease of scalability. This study investigates Na||Sb-Bi batteries consisting of liquid Na as the negative electrode hosted within a Ni-foam, a ternary molten chloride salt electrolyte, and liquid Sb-Bi as the positive electrode. The cells were operated at 430 °C to maintain all components in the liquid state, enabling efficient charge transfer but also introducing challenges related to the corrosive nature of liquid Sb-Bi toward the PCC container, in this case stainless steel 316Ti [1]. However, the influence of operating conditions, particularly C-rate, on corrosion and long-term electrochemical performance remains insufficiently understood.
To address this, two identical Na||Sb-Bi cells with a nominal capacity of 5.6 Ah were assembled and cycled for approximately 1300 h under constant current and temperature at two different C-rates of 0.1C and 1C, while key electrochemical parameters were continuously monitored. Both cells exhibited stable coulombic efficiencies >96%, while energy efficiencies reached 89% at 0.1C and 52% at 1C. ... mehr

Post-mortem analyses revealed differences in surface features of the PCC containers between the cells cycled at different C-rates, along with evidence of Na loss. Metallographic examinations were subsequently conducted to evaluate corrosion mechanisms and related phenomena, such as wall climbing. These findings provide insight into how operating conditions influence corrosion behavior and related performance changes in liquid metal batteries.