A sodium–sulfur (NaS) battery is a type of molten-salt battery that uses liquid sodium and liquid sulfur electrodes. This type of battery has a similar energy density to lithium-ion batteries, and is fabricated from inexpensive and low-toxicity materials.
Utility-scale sodium–sulfur batteries are manufactured by only one company, NGK Insulators Limited (Nagoya, Japan), which currently has an annual production capacity of 90 MW . The sodium sulfur battery is a high-temperature battery. It operates at 300°C and utilizes a solid electrolyte, making it unique among the common secondary cells.
Sodium–sulfur (Na–S) batteries are considered as a promising successor to the next-generation of high-capacity, low-cost and environmentally friendly sulfur-based battery systems.
The sodium–sulfur battery uses sulfur combined with sodium to reversibly charge and discharge, using sodium ions layered in aluminum oxide within the battery's core. The battery shows potential to store lots of energy in small space.
The review focuses on the progress, prospects and challenges of sodium-sulfur batteries operating at high temperature (~ 300 °C). This paper also includes the recent development and progress of room temperature sodium-sulfur batteries. 1. Introduction
In sodium-sulfur batteries, the electrolyte is in solid state but both electrodes are in molten states—i.e., molten sodium and molten sulfur as electrodes.