Sodium-Sulfur Flow Battery for Low-Cost Electrical Storage

A new sodium-sulfur (Na-S) flow battery utilizing molten sodium metal and flowable sulfur-based suspension as electrodes is demonstrated and analyzed for the first time. Unlike the conventional flow battery and the high-temperature Na-S battery, the proposed flow battery system decouples the energy and power thermal management by operating at different temperatures for the storage tank (near room temperature) and the power stack (100-150 degrees C). The new Na-S flow battery offers several advantages such as easy preparation and integration of the electrode, low energy efficiency loss due to temperature maintenance, great tolerance of the volume change of the metal anode, and efficient utilization of sulfur. The Na-S flow battery has an estimated system cost in the range of $50-100 kWh(-1) which is very competitive for grid-scale energy storage applications.